





























































































HKKSHNTK1) in' 





The D. Van Nostrand Company 

intend this book to be sold to the Public 
at the advertised price, and supply it to 
the Trade on terms which will not allow 
of reduction. 









ELECTRIC RAILWAY 


ENGINEERING 


















ELECTRIC RAILWAY 

» 

ENGINEERING 




.a 


its. 


BY 


H. F. PARSHALL., M.Inst.C.E. 

// 


CONSULTING ENGINEER 

A " D 

prT M. HOBART, M.I.E.E. 

» 

CONSULTING ENGINEER 



■0 


t » 


NEW YORK. 

D. VAN NOSTRAND COMPANY 

23,'MURRAY, AND 27, WARREN STREETS 





















v i'i,invot§n a w 







G,. 

C’ct. 31 2 935 





Preface 


The introduction of electricity into railway working, greatly widens the scope of 
electrical engineering. Heretofore the application of electricity has been of a com¬ 
paratively limited nature, since the amount of power that may be usefully applied 
for lighting, traction, or industrial purposes is largely limited by, and commensurate 
with, the population served. In the case of railway working these limitations do not 
exist. There are practically no limitations as to the amount of power or the distance 
to which it may he transmitted, other than those imposed by competition between 
steam and electric traction. 

While the mechanical fitness of an electrical system has been proved by such 
installations as the Baltimore Tunnel, the New York New Haven and Hartford Rail¬ 
way, the New York Central, the North-Eastern, the Lancashire and Yorkshire, and the 
Central London Railway, the commercial limitations imposed by its relatively greater 
first cost have yet to be demonstrated. The installations under construction, like 
those of the New York Central, the New York New Haven and Hartford, and 
the Pennsylvania Railways, will go far towards demonstrating the extent to which 
electric traction may compete with the steam locomotive. 

The considerations which have led to the adoption of electric traction on the larger 
steam railways have generally been peculiar to the local circumstances. For instance* 
in the cases of the Baltimore Tunnel and the New York Central Railway the first con¬ 
sideration was to avoid the smoke nuisance in tunnels. With regard to the latter railway, 
once the necessity for electric traction had been realised, the question of additional 
improvements was taken into consideration, and such elaborate alterations to sidings, 
stations, and terminal arrangements were deemed advisable to suit the more rapid 
electrical working, that the cost as a whole was several times that necessarily incident 
to the change from steam to electricity. 

The electrical installation must of necessity, to compete with steam, be capable of 
dealing with a greater maximum demand per hour in passenger accommodation, since, 
with its power station, transforming system, and train equipment, it is of greater cost 
than the steam locomotive. The electrical installation, with its higher speeds and 
better acceleration, possesses greater mobility than a steam equipment, and the train 
may be easily split up into self-contained units to suit the varying demands of the 
traffic. Except in the case of exceedingly dense and steady traffic, the cost of working 
by electricity will, apparently for a long time to come, be greater than that of working 
by steam. It frequently happens in railway working that the advantages or dis¬ 
advantages of a particular kind of train service for working in or about the terminus 
of a great railway should not be dealt with by themselves, but rather as a feature of 
the system in its entirety. Thus it often occurs that the commercial limitations of a 
railway are determined by the facilities at its termini, and that improved facilities may 
mean an increase in the earning capacity of the line. Frequently the operation of 
main line trains is limited by the necessities of local traffic. There are numerous 
cases of this description where electricity may be relied upon to improve the condition 
of a system as a whole, although the local commercial advantages, taking the increased 


v 


PREFACE 


cost as compared with the increased local traffic, are not at first apparent. These 
distances will undoubtedly extend as time goes on, since, with the great improvements 
being effected in steam-driven generating apparatus, the higher pressures at which 
motors may be safely worked, and the redistribution of population incident to more 
rapid transit, the conditions now deemed favourable for electrical working on short 
lines will become common on lines extending over considerable distances. 

In the application of electricity to long distance lines, it is to be steadily borne in 
mind that the steam locomotive has demonstrated itself to be the most efficient 
self-contained machine, considering its varying functions, that the engineer has yet 
devised, and that, to compete with this machine, every appliance entering into the 
electric traction installation must compare from every point of view, as regards 
efficiency, with this most highly developed and perfect mechanism, and that the 
electric locomotive installation duplicates, in many respects, the steam locomotive 
installation. 

It is not our purpose to undertake to predict the form that the ultimate electric 
railway installation may assume. Standardisation has been one of the great elements 
of success in steam railway working, and the future growth of electric traction will he 
slow until the standardisation phase has been reached. At the present time there exists 
a wide difference of opinion among engineers as regards the commercial advantages of 
alternating current and continuous current motors for traction. In our judgment, the 
limitation of the alternating current motor is fixed, in its relation of energy output to 
weight, by the inherent properties of single-phase commutator apparatus, and that the 
limitation of the continuous current motor will be determined by the maximum safe 
voltage at which a commutating machine can be worked. While the development of 
each class of machine has advanced beyond the point that could reasonably have been 
foreseen, and while in our judgment it is impossible at the present time to predict 
where the limitations will be reached, we are satisfied that a careful comparison of 
the two types at the present time is decidedly to the advantage of the high tension 
continuous current motor. The primary mechanical advantage of electric traction 
is obtained with either class of apparatus, owing to the fact that power may be 
distributed over the train and applied to as many axles as may be necessary to 
secure the best mechanical result. 

There is not much to choose between the methods of control as between 
alternating current and continuous current, and in the main the points to he proved 
in the working of the two systems will be found to lie in the maintenance of the 
motor and train equipments. The terms adopted in the comparison of the properties 
of the two classes of machines leave much to be desired. In the maintenance of a 
train equipment a serious item is that of keeping the armature central in the 
fields; hence it is fundamental that motors of like power should, when compared, have 
the same mechanical characteristics as regards weight and speed of rotor, and 
mechanical clearance. Another condition we would emphasise is that for the same 
speed the motors should have the same torque per ampere intake, and the same 
percentage of line voltage at the terminals. We are tempted to emphasise this point, 
since it is entirely misleading to the railway engineer to compare the electrical results 
without making mention of mechanical and other differences that primarily affect the 
whole question of operation and maintenance. 

With the gradual extension of the application of electricity for all purposes along 
the different railway systems, the distance to which electrical working becomes 

vi 


PREFACE 


profitable, will be extended, and with the installation of such power systems as are 
now becoming common in Great Britain, it would appear that the distance may be 
indefinitely extended. 

The advantages of electric traction, like those of the central power installation, 
increase with the magnitude. The diversity and load factors increase therewith, as 
also the various economies incidental to an improved load factor. As an ultimate 
result, freight haulage may be anticipated. The electrical output per mile of track 
must be considerable to bring the cost of haulage per ton-mile by electricity to that 
now common by steam. 

In the following pages we have endeavoured to place in an accessible form, a portion 
of the results of our own observations and experience in this most important department 
of engineering, and we have referred to and quoted from the work of other writers in 
instances where the usefulness of the book is thereby increased. We fully realise that the 
book is incomplete in many respects, but having regard to the amount of time already 
taken in its preparation, further delay in its publication does not seem warranted. 

The authors wish to take this opportunity of making due acknowledgment of the 
assistance rendered them by engineers, technical journals, manufacturers, and others. 

In the former class should be mentioned Messrs. Evan Parry, W. Casson, F. W. 
Carter, Prof. Ernest Wilson, F. Punga, A. S. Garfield, T. Stevens, B. Yalatin. 
C. W. G. Little, P. von Kalnassy, W. C. Gotsball, W. M. Camp, 0 . Lasche, G. 
Wuthrich, and A. G. Ellis. 

A number of manufacturing and operating companies have kindly supplied us 
with valuable data. Amongst others may be mentioned Messrs. The Oerlikon Co., 
The British Thomson-Houston Co., The British Westingliouse Co., Ganz & Co., The 
Brush Electrical Engineering Co., and the Interborough Rapid Transit Co. of 
New York. 

Amongst the technical periodicals which have extended us courtesies in the 
supplying of data, and in granting permission to quote from their columns, we would 
mention The Street Railway Journal, The Electrical Review, The Electrician, The 
Tramway and Railway World, The Engineer, Engineering, The Light Railway and 
Tramway Journal, Elektrotechnische Zeitschrift, Zeitschrift des Vereines Deutscher 
Ingenieure, and Elektrische Bahnen und Betriebe. 

For permission to quote from their proceedings we have to express our thanks to 
the Institutions of Civil Engineers, Electrical Engineers, Mechanical Engineers, and 
the American Institutes of Electrical Engineers and Mining Engineers. 






Table of Contents 


PAGE 

Preface . v 

PART I 

THE MECHANICS OF ELECTRIC TRACTION 

CHAPTER I 

Tractive Resistance at Constant Speed. 3 


Acceleration 

CHAPTER II 

.21 


CHAPTER III 


The Tractive Force and the Power and Energy at the Axles ...... 40 

CHAPTER IV 

The Study of the Characteristics of Electric Railway Motors, and of Section 

Characteristics and the Construction of Load Curves ...... 54 

PART II 

THE GENERATION AND TRANSMISSION OF THE ELECTRICAL ENERGY 

CHAPTER V 

The Electrical Power Generating Plant. 101 

CHAPTER VI 

The High Tension Transmission System. 140 


The Sub-stations 

CHAPTER VII 

.172 


CHAPTER VIII 


The Distributing System 


244 


TABLE OF CONTENTS 


PART III 

THE ROLLING STOCK 


CHAPTER IX 

Locomotives and Motor Carriages and their Electrical Equipment 


page 

291 


CHAPTER X 


Trucks . ....... 430 


INDEX 


465 


List of Illustrations 


PART i 

THE MECHANICS OF ELECTRIC TRACTION 

FIG - PAGE 

1. Curves of Tractive Resistance at Low Speeds for an 83-Ton 75-foot Car, as deduced from 

the Berlin-Zossen Tests ............. 4 

2 . Curves of Tractive Resistance for Various Lengths of Train ...... Q 

3. Curves of Tractive Resistance for 83-Ton 75-foot Car ........ 7 

4. Curves for Tractive Resistance according to well-known Formulae. Single Car Operation. 

Weight of Car about 22 Tons ............ g 

5. Same as Fig. 4, but for Train of Five 40-Ton Carriages, say 200 Tons ..... 9 

6 . Curves of Tractive Resistance in Tube Railways ........ 9 

7. Curves of Tractive Resistance in Tube Railways and on Surface ...... 10 

8 . Curves of Component and Resultant Tractive Resistance for 83-Ton 75-foot Car, deduced 

from Berlin-Zossen Tests ............. n 

9. Percentage of Passenger Weight to Total Train Weight (Grand Central Station to Mott 

Haven Junction) .............. 12 

10. Curves of Tractive Resistance in Pounds per Ton for Various Speeds in Miles per Hour . 15 

11. Curves of Tractive Resistance in Pounds per Ton for Various Speeds in Feet per Second . 16 

12. Curves of Power in Kilowatts at the Axles per Ton Weight of Train ..... 16 

13. Curves of Total Power in Kilowatts at Axles ......... 17 

14. Carter’s Train Resistance Curves, giving the Variable Component of Train Resistance . 18 

15. (A, B, C, D, E, and F). Speed, distance, and time Curves for Various Accelerations To face 22 

16 Speed-distance-time Curves (Armstrong’s) .......... 23 

17. Speed-distance-time Curves ............. 24 

18. (A, B, and C). Speed-distance-time Curves for a 1-mile Run at an Average Speed of 

30 Miles per Hour. Time from Start to Stop = 2 Minutes ...... 25 

19. Speed-time and Distance-time Curves for Various Accelerations and Average Speeds. 

^-mile Run ............. To face 26 

20. Speed-time and Distance-time Curves for Various Accelerations and Average Speeds. 

1- mile Run ............. To face 26 

21 . Speed-time and Distance-time Curves for Various Accelerations and Average Speeds. 

2- mile Run ............. To face 26 

22. Speed-time and Distance-time Curves for Various Accelerations and Average Speeds. 

4-mile Run ............. To face 26 

23. Speed-time and Distance-time Curves for Various Accelerations and Average Speeds. 

8 -mile Run ............. To face 26 

24. Maximum Speeds for Different Lengths of Sections and Various Accelerations and Schedule 

Speeds, and Various Durations of Stop ' . . . . . . . . . .27 

25. Curves of Acceleration and Schedule Speed for Various Distances between Stops To face 28 

26. Curves of Limiting Attainable Schedule Speeds for given Mean Rates of Acceleration and 

Braking ............ ... 30 

27. Speed-time Curve for a 65 (Metric) Ton Electric Train of Motor Cars (no Trailers) . . 31 

28. Speed-time Curve for a Constant Acceleration of 2 - 2 Miles per Hour per Second. Average 

Speed 40 Miles per Hour.31 

29. Speed-time Curves for a Mean Acceleration of 2'2 Miles per Hour per Second. Average 

Speed 40 Miles per Hour . ..31 

30. To Illustrate Case of Running on “ Motor Curve ”.32 


xi 



LIST OF ILLUSTRATIONS 


FIG. PAGE 

31. Speed-time and Speed-distance Curves for an Average Speed of 40 Miles per Hour for 

Runs of Various Lengths ............. 33 

32. Speed-time-distance Curves for an Average Speed of 60 Miles per Hour for 2, 4, and 

8 -mile Runs from Start to Stop ........... 35 

33. Speed-distance-time Curves for 4-mile Section ......... 36 

34. Values of and G f ~ .38 

V av. T> 

35. Charts showing Tractive Force with Various Accelerating Rates for Trains of Different 

Weights ................ 40 

36. Charts showing Tractive Force with Various Accelerating Rates for 200-ton Train . . 41 

37. Curves of Speed, Tractive Force, Power, and Energy at Axle. 200-ton Train operated 

between Stops at an Average Speed of 30 Miles per Hour, with One Stop per Mile . 42 

38. Curve of Watt-hours at Axles per Ton-Mile for 200-ton Train operating with One Stop per 

Mile at an Average Speed of 30 Miles per Hour between Stops, and with Varying Rates 
of Acceleration ............... 43 


39. Curve of Maximum Instantaneous Power at Axles in Kilowatts per Ton Weight of Train. 
200-ton Train operated with One Stop per Mile at an Average Speed of 30 Miles per 


Hour between Stops for Different Rates of Uniform Acceleration. Rate of Retardation 
taken as equal to Rate of Acceleration .......... 44 

40. Curve of Average Power from Start to Stop in Kilowatts at Axles per Ton Weight of 

Train operated with One Stop per Mile at an Average Speed of 30 Miles per Hour 
between Stops, for Different Rates of Uniform Acceleration ...... 44 

41. Curves for Tramcar operated on Ordinary Series Parallel and on Regenerative Control 

Systems ................ 46 

42. Tramcar Relative Inputs at Different Speeds on Level Track ...... 47 

43. Curves of Energy and Maximum Instantaneous Power at Axles ...... 48 

44. Curves of Energy required at Axles of 200-Ton Train for Various Lengths of Run and 

Schedule Speeds ............... 49 

45. Curves of Energy Input to 200-Ton Train for Various Lengths of Run and Schedule 

Speeds ................ 50 

46. Curves showing Relation between the Accelerating Rate and the Ratio of the Maximum 

to the Average Power at the Axles. 200-Ton Train operated with One Stop per Two Miles, 
at an Average Speed of 30 Miles per Hour between Stops ...... 50 

47. Typical Train Characteristic (S.T.) Curves for Trains operated by Continuous Current . 51 

48. Typical Train Characteristic (S.T.) Curves for Continuous Current Equipments . . 52 

49. To explain Connection between Speed and Input of Ideal Series Motors .... 55 

50. Curves showing Efficiency, Speed, and Tractive Force of G.E. 66 A. Motor of 125 H.-P. 

Rated Output ............... 56 

51. To explain Connection between Speed and Input of G.E. 66 A. Motor . .... 58 

52. To explain Connection between Tractive Force and Input using Four G.E. 66 A. Motors . 60 

53. To explain Connection between Tractive Force (Curve I.), Initial Accelerating Rate 

(Curve II.) and Input, using Four G.E. 66 A. Motors ....... 61 

54 to 59. Acceleration-current-speed-time Curves for Four G.E. 66 A. Motors in Parallel 

To face 62 

60. Characteristic Curves of Parallel Operation of Four G.E. 66 A. Motors .... 64 

61. Characteristic Curves of Parallel Operation of Four G.E. 66 A. Motors .... 65 

62 and 63. Characteristic Curves of Parallel Operation of Four G.E. 66 A. Motors ... 66 

64 to 66 . Acceleration-current-speed-time Curves for Four G.E. 66 A. Motors in Parallel 

To face 66 

67 to 70. Acceleration-current-speed-distance-time Curves for Four G.E. 66 A. Motors in 

Parallel. To face 66 

71. Curves Allocating the Distribution of the Energy with Four 66 A. Motors in Parallel . . 68 

72. Curves of Input and Output for Four G.E. 66 A. Motors in Parallel.70 

73 to 75. Speed, Tractive Force, and Power Curves for Four G.E. 66 A. Motors in Parallel and 

assuming Straight Line Acceleration and Retardation . . . . . . .71 

' 76. Series Parallel Operation of Four G.E. 66 A. Motors . ..72 

xii 




LIST OF ILLUSTRATIONS 


FIG. PAGE 

77. Characteristic Curves of Series Parallel Operation of Four G.E. 66 A. Motors, with a Gear 

Ratio of 3 - 94, and with 34 in. Driving Wheels. 125-Ton Train. Level Track To face 72 
78 to 80 and 84. Relating to Method of Series-Parallel Control corresponding to Method B. of 

Table XX. ............. To face 72 

81 to 83 and 85. Relating to Method of Series-Parallel Control corresponding to Method C. of 

Table XX. ............. To face 72 

86 to 89. Time-tractive Force Speed Curves ........ To face 76 

90. Characteristic Curves for a 4-mile Run at an Average Speed of 19 Miles per Hour. 120-Ton 

Train. Level Track. No Coasting ........... 77 

91. Characteristic Curves for a 4-mile Run at an Average Speed of 18 - 1 Miles per Hour. 

120-Ton Train. Level Track. Coasting for 39 Seconds.78 

92. Characteristic Curves for a 4-mile Run at an Average Speed of 16 - 1 Miles per Hour. 

120-Ton Train. Level Track. Coasting for 72 Seconds ...... 78 

93. Characteristic Curves for a 4-oiile Run at an Average Speed of 13 - 4 Miles per Hour. 

120-Ton Train. Level Track. Coasting for 107 Seconds ...... 79 

94. Characteristic Curves for a 4-mile Run at an Average Speed of 19 Miles per Hour, and 

with Coasting for 23 Seconds. 120-Ton Train. Level Track . . .To face 80 

95. Characteristic Curves for a J-mile Run at an Average Speed of 19 Miles per Hour, and 

with Coasting for 32 Seconds. 120-Ton Train. Level Track ... To face 80 

96. Characteristic Curves for a 4-mile Run at an Average Speed of 19 Miles per Hour. 120-Ton 

Train. Grades as set forth in Table XXIV. ....... To face 80 

97. Characteristic Curves of G.E. 66 A. Motor for three different Gear Ratios . To face 82 

98. Characteristic Curves of Series Parallel Operation of four G.E. 66 A. Motors with a Gear 

Ratio of 4 - 73, and with 34-inch Driving "Wheels. 125-Ton Train. Level Track To face 82 

99. Typical Temperature Curve for an intermittently-loaded Motor...... 83 

100. Curve showing the Temperature Rise of a Railway Motor when running on a Service with 

long Coasts and frequent Stops ......... To face 84 

101. The Effect of frequent Stops in High Speed Railroading (A. H. Armstrong, Street Railway 

Journal, Vol. XXIII., p. 70, January 9th, 1904) ........ 85 

102. Energy Consumption for a 32-Ton Car at Various Schedule Speeds . .... 86 

103. Carter’s Curve of Rated Capacity of Electrical Equipment ...... 87 

104. Curves for deriving the Kilo watts Input per Ton to a 30-Ton Car for Various Schedule 

Speeds and Various Stops per Mile. Duration of Stop = 20 Seconds .... 89 

105. Armstrong’s Curves for showing the variations in Train Resistance with Size and Speed 

of Train. To face 89 

106. Curves of Tractive Resistance for Single Cars of Various Weights according to Wynne 

(Blood’s Formula) .............. 90 

107. Curves compiled from Carter’s Data on Weights of Continuous Current Equipments . 92 

108. Curves of Total Energy Consumption at the Contact Shoe per Ton-mile .... 93 


PART II 

THE GENERATION AND TRANSMISSION OF THE ELECTRICAL ENERGY 


109. Central London Railway : Daily Load Curve ......... 102 

110. Diagram for Estimating Condenser Capacities ..... ■ To face 114 

111. Central London Railway : Plan of Power Station ........ 116 

112. Central London Railway : Cross-section of Power Station . ...... 117 

113. Glasgow Corporation Tramways : Plan of Power Station ..... To face 120 

114. Glasgow Corporation Tramways : Cross-section of Power Station ..... 121 

115. Bristol Tramways : Cross-section of Power Station ........ 125 

116. Dublin United Tramways : Cross-section of Power Station ...... 128 

117. Arrangement of Boiler Plant of Dublin United Tramways Generating Station . To face 128 

118. Plan of Engine Room of Dublin United Tramways Generating Station . . To face 128 

xiii 





LIST OF ILLUSTRATIONS 


FIG. PAGE 

119. Design of 10,000-k.w. Power Station. Plan ......... 131 

120. Design of 10,000-k.w. Power Station. Cross-section ........ 132 

121. Comparison of Efficiencies of English and Foreign Electrical Generating Stations . 135 

122. Costs of High-tension Three-core Cables 143 

123. Curves showing the Ratio of the Cost of Three-core Cables complete, to the Cost of 

Copper contained in the Three Cores for 500 to 20,000 Volts between Cores . . . 144 

124. Costs of Cables for Transmission Lines, for transmitting 1,000 to 16,000 k.w. to a distance 

of 10 to 14 kilometres at Power Factors of 1*0 and 0'8 ..... To face 144 
125 to 128. Curves showing Minimum Costs of Cables for transmitting 1,000 to 8,000 k.w. to a 

Distance of 10 to 40 kilometres . . . . . . ■ . . . 146 

129. Kavanagh’s Curves of Current Densities in Cables ........ 150 

130. Current-caiTying Capacity of British Standard Cables ....... 151 

131. Ferguson’s Tests of Temperature Distribution in Cables ....... 152 

132 and 133. Ferguson’s Curves showing Temperature Rise in Cables ..... 152 

134. New York Subway : Arrangement of Cable Ducts under Street ..... 154 

135. New York Subway: Location and Arrangement of Cable Ducts inside Wall of Tunnel . 154 

136. New York Subway: Arrangement of Cable Ducts under Passenger Station . . 155 

137. New York Subway : Arrangement of Cables in Manhole ....... 156 

138. New York Subway : Cable ............ 157 

139. Arrangement of Central London Railway Cables ........ 157 

140. District Railway: Cables Mounted on Wall, showing Joints ...... 159 

141. District Railway: Section through High Tension Cable-Joint .... . 160 

142. District Railway : Manhole in Transmission Line under Construction .... 161 

143. Sections of Various High-tension Cables ....... To face 162 

144. Section of Henley’s Patent Laminae Conductor Three-core Cable ..... 162 

145. Curve showing Voltage required at Generator for 23,100 Volts per Phase at Receiving End 

with Different Power Factors ............ 170 

145a. New York Central Railway : Plan, Elevation, and Sections of Pole for Transmission 

Lines ................ 170 

146 to 148. Phase Characteristics of Hypothetical Synchronous Motors . . . . .174 

149. Phase Characteristics of Synchronous Motor for 900-k.w. Input at Rated Load . . 176 

150. Saturation Curve of a 600-k.w. Rotary Converter ........ 178 

151. Curves showing Amperes Input per Phase at Various Loads of a 600-k.w. Rotary Converter . 179 

152. 158 and 159. Curves of Efficiency and Power Factor of a 600-k.w. Rotary Converter 

To face 182 

153 to 157. Diagram for determining Generator Voltage at Various Loads .... 181 

160 to 163. Rotary Converter Compounding Curves ....... To face 186 

164 and 165. Rotary Converter Regulation Curves ....... To face 188 

166 and 167. Full Load Voltages at Commutators of Rotary Converters . . . To face 188 

168. 400-k.w. Rotary Converter Characteristic Phase Curves ....... 189 

169. Booster Volt-ampere Characteristic Curves ........ 193 

170. Battery Volt-ampere Characteristic Curves ......... 193 

171. Connection Diagram for Battery-Booster Set in Parallel with Two Shunt-wound Rotary 

Converters ............... 194 

172. Curves of Regulation of Rotary Converter, Battery, and Booster ..... 194 

173. Diagrams showing Subdivision of the Current between Rotaries and Battery 195 

174. Curves showing Distribution of Load between Rotaries and Battery Booster 195 

175. Five Minutes Load Curve ... ......... 196 

176. Connections of Three-phase Rotary with Compensator ....... 205 

177. Diagram of Connections for Synchronising and Switching applicable to Six-phase Rotary 

Converters ............... 207 

178. Diagram of Connections applicable to Three-phase Rotaries ...... 207 

179. Central London Railway : General Arrangement of Marble Arch Sub-station . To face 208 

180. Central London Railway : Notting Hill Gate Sub-station Main Switchboard . . . 213 

181. Central London Railway : Diagram of Connections of Two Sub-stations . . To face 212 

182. Central London Railway : Arrangement of High Tension Bus Bars and Ammeter Trans¬ 

former . ...213 


Xiv 





LIST OF ILLUSTRATIONS 


FIG. PAGE 

183. Central London Railway: Back View of Sub station Switchboard. High Tension and Low 

Tension Feeder Panels ............. 214 

184. Central London Railway: Back View of Sub-station Switchboard. Transformer and 

Converter Panels .............. 214 

184a. Central London Railway: Front View of High Tension Panels, showing Three-phase 

Switch.215 

185. Central London Railway: Notting Hill Gate Sub-station. Bank of 800-k.w. 

Transformers ............... 216 

186. Central London Railway: Notting Hill Gate Sub-station. 300-k.w. Transformer, 

Elevations and Plan ............ 217 

187. 300-k.w. Central London Railway Transformer, Efficiency and Losses .... 217 

188. Central London Railway: Samuelson’s Triple Pole Quick Brake Switch for Rotary 

Convei’ter................ 218 

189. Central London Railway : 900-k.w. Rotai-y Converter ..... To face 218 

190. Central London Railway: 900-k.w. Rotai'y Converter ....... 219 

191. Central London Railway: Curves of Efficiency and Losses of 900-k.w. Rotary Converter . 219 

192. Central London Railway : Magnetisation Curve of 900-k.w. Rotary Converter . . . 220 

193. Central London Railway : Phase Characteristic of 900-k.w. Rotary Converter . . . 220 

194. Metropolitan Railway : Ruislip and Harrow Sub-stations ....... 222 

195. Metropolitan Railway : Ruislip and Harrow Sub-stations ....... 223 

196. District Railway : Plan of Charing Cross Sub-station ...... 224 

197. District Railway : Gallery Elevation, Charing Cross Sub-station ..... 225 

198. District Railway : Diagram of Connections at Charing Cross Sub-station . . . 226 

199. District Railway: Putney Bridge Sub-station Switchboard ...... 227 

200. District Railway : Type C. Oil Switch in Sub-station ....... 228 

201. North-Eastern Railway : Ground Plan of Typical Sub-station ..... 229 

202. North-Eastern Railway: Longitudinal Section of Sub-station ..... 230 

203. North-Eastern Railway : Cross Section of Sub-station ....... 230 

204. North-Eastern Railway: Westinghouse Oil-Break High Tension Switches . . . 231 

205. North-Eastern Railway : Electrical Connections at Pandon Dene Sub-station . . . 233 

206. New York Subway : Converter Floor Plan of Sub-station No. 14 .... 237 

207. New York Subway : Cross Section of Sub-station No. 14 ...... 238 

208. New York Subway : Longitudinal Section of Sub-station No. 14 .... 239 

209. New York Subway: Operating Gallery in Sub-station .... . . 240 

210. Curve for Resistance and Composition of Steel ......... 246 

211. Curves showing the Effect of Carbon and Manganese on the Conductivity of Steel . . 247 

212. Methods of Mounting and Insulating Conductor Rails ....... 250 

213. Conductor Rail Insulator. London Underground Electric Railways Co. .... 250 

214. Pedestal Type of Rail Insulator ............ 251 

215. Reconstructed Granite Co.’s Insulators .......... 252 

216. Chambers’ Patent Third Rail Insulator .... ..... 253 

217. Methods of Protecting Conductor Rails .......... 253 

218. N.Y.C. Showing Arrangement of Under Contact Third Rail ...... 254 

219. The Farnham “ Under Contact ” Protected Third Rail System .... 255 

220. Sections of Single Track on Various Railways ....... To face 256 

221. Sections of Double Track on Various Railways ......... 257 

222. Sections of Various Types of Conductor and Track Rails in Common Use . . . . 258 

223. Photograph showing Single Cable Susj:>ension with Side Poles as erected by the Westing- 

house Co. ............... 261 

224. Photograph showing Double Cable Suspension supported from Gantries constructed by 

the Westinghouse Co. ............. 262 

225. Side Pole Single Insulation, Single Cable Suspension. (British Thomson-Houston Co.) . 263 

226. Side Pole Double Insulation Single Cable Suspension with Vertically Yielding Anchorage. 

(British Thomson-Houston Co.).264 

227. Side Pole and Bracket Arm, with Insulators and Stay. (British Westinghouse Co.) . 265 

228. Bracket Arm Insulator. (British Westinghouse Co.).265 

229. Insulated Stay for Trolley Wire for attaching to Bracket Arm. (British Westinghouse Co.) 266 

XV 



LIST OF ILLUSTRATIONS 

FIG. PAGE 

230. Section Insulator. (British Westinghouse Co.) 266 

231. Method of Sectionalising Conductor. (British Thomson-Houston Co.) .... 267 

232. Hanger of Suspender. (British Westinghouse Co.) ..•••••• 268 

233. Curve Pull-off. (British Westinghouse Co.) 268 

234. Gantry for Two Tracks, supporting Two Conductors on the Single Cable Principle with 

Double Insulation. (British Thomson-Houston Co.) .....•• 268 

235. Gantry Constructions for Two, Four, and Six Tracks, with Double Cable Suspension. 

(British Thomson-Houston Co.) ......... To face 268 

236. Engineering Standards. Committee Standard Sections . . . • • • .270 

237. General Electric Co. (U.S.A.) Bail Bond : Section through Bond, showing Effect of 

Compression ............... 273 

238. General Electric Co. Type of Bond, Protected by Fishplate .... 274 

239. General Electric Co. Type of Bond under Sole of Bail . .274 

240. General Electric Co. Bond outside Fishplate . . .274 

241. Bail Bonding Press ........ .274 

242. Forest City Electric Co.’s Protected Bond ...... .275 

243. Protected Type Bail Bond under Fishplate ...... .276 

244. Protected Type of Bonds on London Underground Electric Bail ways 276 

245. Protected Type of Bond on London Underground Electric Bailways . . 276 

246. Chicago Bail Bond .......... . 277 

247. Crown Bail Bond ..... 277 

248. Columbia Bail Bond ........ ..... 277 

249. Thomas’ Soldered Bail Bonds .... .... 278 

250. Shawmut Soldered Bail Bond ...... .278 

251. Arrangement of Track Boosters for Alternating Currents ....... 284 

PART III 

THE ROLLING STOCK 

252. Electric Locomotive for New York Central Bailroad. Weight, 85 Metric Tons . . 291 

253. Electric Locomotive for New York Central Bailroad. Weight, 85 Metric Tons . 292 

254. Assembly of Truck of New York Central Locomotive ....... 294 

255. Motor Armature of New York Central Locomotive .... . . 295 

256. Sectional View of Air Compressor for New York Central Locomotive . 296 

257. Third Bail Shoe of New York Central Locomotive ........ 297 

258. Overhead Contact Device of New York Central Locomotive . . 297 

259. Characteristic Curves of New York Central Locomotive ....... 298 

260. Curves of Current Input, Voltage and Speed of New York Central Locomotive with Eight- 

Car Train................ 299 

261. Curves of Current Input, Voltage and Speed of New York Central Locomotive with Four- 

Car Train.299 

262. New York Central Locomotive hauling a Six-car Train during one of the Tests of 

November, 1904 .............. 300 

263. Profile of Alignment and Grades of New York Central Experimental Track . . 301 

264. Diagram of Governing Dimensions and Weights of New York Central Steam and Electric 

Locomotives employed in Tests made April 29th, 1905 ....... 302 

265. Acceleration and Speed-time Curves for Bun D of New York Central Locomotive Tests . 305 

266. Acceleration Test on New York Central Electric Locomotive hauling a Train of Eleven Cars 306 

267. Speed Bun of New York Central Electric Locomotive hauling a Train of Eleven Cars . 306 

268. Baltimore and Ohio 1896 Gearless Six-pole Locomotive. Complete Weight, 87 Metric Tons 308 

268a. Truck of Baltimore and Ohio 1896 Gearless Locomotive, showing Motor in Place . . 309 

269. One Component of 1903 Baltimore and Ohio Locomotive ....... 310 

270. Baltimore and Ohio Two-unit 1903 Locomotive, with Geared Four-pole Motors, Weight of 

Two-unit Combination, 146 Tons . . . . . . . . .311 

271. Interior of One-unit of Baltimore and Ohio 1903 Electric Locomotive .... 312 

xvi 




LIST OF ILLUSTRATIONS 


272. Frame of One-unit of Baltimore and Ohio 1903 Electric Locomotive. 813 

273. Character Curves of Baltimore and Ohio 1903 Geared Two-unit Locomotive . . . 315 

274. Method of mounting Armature on Axle of City and South London Bail way Gearless 

Locomotive ............... 315 

275. City and South London Gearless Locomotive ........ 316 

276. Central London Railway Gearless Locomotive ...... 318 

277. 49 Metric-ton Paris-Orleans Geared Electric Locomotive ....... 320 

278. Paris-Orleans Geared Electric Locomotive .......... 321 

279. Characteristic Curves of Paris-Orleans Locomotive with 4 - l Gear Ratio .... 322 

280. Characteristic Curves of Paris-Orleans Electric Locomotives with 2'23 Gear Ratio . . 323 

281. “ Baggage-car.” Type of Paris-Orleans Electric Locomotive . . ... 324 

282. Early Type of Valtellina Three-Phase Gearless Locomotive ...... 327 

283. Early Type of Valtellina (Gearless) Locomotive. To face 328 

284. Early Type of Valtellina (Gearless) Locomotive. To face 328 

285. Early Type of Valtellina (Gearless) Locomotive ... 328 

286. Early Type of Valtellina (Gearless) Locomotive. 329 

287. “ 1904 ” Type of Valtellina Locomotive .... 330 

288. “ 1904 ” Type Valtellina Three-Phase Electric Locomotive ... 331 

289. “ 1904 Type Valtellina Three-Phase Electric Locomotive ...... 332 

290. “ 1904 ” Type Valtellina Three-Phase Electric Locomotive ...... 333 

291. “ 1904 ” Type Valtellina Three-Phase Electric Locomotive ...... 333 

292. “ 1904 ” Type Valtellina Three-Phase Electric Locomotive ...... 334 

293. Trolley for “ 1904 ” Type Valtellina Three-Phase Electric Locomotive .... 335 

294. Interior of Driver’s Cab of “ 1904 ” Valtellina Locomotive ...... 336 

295. Electrical Connections of “ 1904 ” Type Valtellina Three-Phase Electric Locomotive 

To face 336 

296. Communicating Bearing between Crank and Connecting Rod on “ 1904 ” Type Valtellina 

Three-Phase Locomotive ..... ....... 337 

297. One of the Cascade Motor Sets of the “ 1904 ” Type Valtellina Three-Phase Electric 

Locomotive ............... 337 

298. Outline Drawings of one of the Cascade Motor Sets of the “ 1904 ” Type Valtellina 

Three-Phase Electric Locomotive ......... To face 336 

299. Showing Slip Rings of Motor of “ 1904 ” Type Valtellina Three-Phase Electric 

Locomotive ............... 338 

300. Diagram of Pneumatic Control Connections for the Water Rheostat Type of Valtellina 

“ 1904 ” Three-Phase Locomotive ........... 339 

301. Diagram of Pneumatic Control Connections for the Metallic Rheostat Type of Valtellina 

“ 1904 ” Three-Phase Locomotive ........... 340 

302. Motor-driven Air Compressor for the “ 1904 ” Type Valtellina Three-Phase Electric 

Locomotive ............... 341 

303. Motor Car of the Valtellina Railway, Equipped with Four Polyphase Motors 342 

304. Three-Phase Motor mounted on Axle of Valtellina Motor Carriage .... 343 

305. Elastic Coupling between Wheel and Motor of Valtellina Motor Carriage .... 344 

306. One of the Bogie Trucks of a Valtellina Motor Carriage, with Three-Phase Motors . . 345 


307. Oerlikon 15,000-volt 15-Cycle Locomotive, equipped with Single-Phase Commutator Motors 345 

308. Oerlikon 15,000-volt 15-Cycle Locomotive, equipped with Single-Phase Commutator Motors 346 

309. Outline Drawings of 200 Kilovolt Ampere Air Blast Transformer, of which two are Installed 

on the Oerlikon 15,000-volt 15-Cycle Locomotive with Single-Phase Commutator Motors 
(Dimensions in Millimetres) ............ 347 

310. 200 h.-p. Single-Phase Commutator Motor with Reversing Poles as Installed on the 

15,000-volt 15-Cycle Oerlikon Locomotive ......... 348 

311. 200 h.-p. Single-Phase Commutator Motor with Reversing Poles, as Installed on the 

15,000-volt 15-Cycle Oerlikon Locomotive ......... 349 

312. Diagram of Principles of Operation of 200 h.-p. Single-phase Interpole Commutator Motors 

of the Type Employed on the Oerlikon 15,000-volt 15-Cycle Locomotive . . . 349 

313. Connection Diagram of Wiring of Oerlikon 15,000-volt 15-Cycle Locomotive with Single- 

Phase Commutator Motors ............ 350 


E.R.E. 


XVII 


b 










LIST OF ILLUSTRATIONS 


FIG. PAGE 

314. Characteristic Curves of Oerlikon 200 h.-p. Single-Phase Commutator Motor (Current 

Constant at 200 Amperes) 350 

315. Characteristic Curves of Oerlikon 200 h.-p. Single-Phase Commutator Motor (Speed 

Constant at 650 R.P.M.) .... .....■• 350 

316. Oerlikon High-Voltage Single-Phase Locomotive of the Motor Generator Type . . • 351 

317. High-Voltage Single-Phase Motor Generator Type Oerlikon Locomotive .... 352 

318. Oerlikon Trolley 352 

319. Oerlikon Trolley 353 

320. Oerlikon Trolley ........ ...... 353 

321. Oerlikon Trolley ............... 354 

322. Oerlikon Overhead High Tension Switch .......... 355 

323. Siemens and Halske High-speed Locomotive, with 10,000-volt Three-Phase Motors . . 356 

324. Siemens and Halske High-speed Locomotive, with 10,000-volt Three-Phase Motors . . 357 

325. Characteristic Curves of 10,000-volt Motors of the Siemens and Halske Loco¬ 

motive ................ 358 

326. Siemens and Halske 10,000-volt Three-Phase Motor ........ 358 

327. Siemens and Halske 10,000-volt Three-Phase Motor ........ 359 

328. Siemens and Halske 10,000-volt Three-Phase Motor ........ 359 

329. Stator of 10,000-volt Siemens and Halske Three-Phase Motor ...... 360 

330. Siemens and Halske 10,000-volt Three-Phase Motor ........ 360 

331. Diagram of Electrical Connections of Siemens and Halske 10,000-volt Three-Phase 

Locomotive ............... 361 

332. Siemens and Halske High-speed Zossen Motor Car ...... To face 362 

333. Siemens and Halske High-speed Zossen Motor Car . . . . . . . 361 

334. A.E.G. High-speed Motor Car ............ 362 

335. AllgemeineElektricitats-Gesellschaft High-speed Motor Car used in Berlin Zossen Trials. 363 

336. S. & H. Motor for High-speed Zossen Motor Car ........ 364 

337. A.E.G. Motor for High-speed Zossen Motor Car ........ 365 

338. Spring Supporting Gear for A.E.G. Motor ......... 365 

339. Rotor of Motor of S. & H. Zossen Motor Car ...... 365 

340. Rotor of Motor of A.E.G. Zossen Motor Car ......... 366 

341. Rotor of Motor of A.E.G. Zossen Car in Place on Axle ....... 366 

342. Stator Core and Secondary Winding of Motor of Siemens and Halske Zossen Motor 

Car.366 

343. Assembled Motor of A.E.G. High-speed Zossen Motor Car ...... 367 

344. Method of Suspending Carriage of Langen Mono-rail System ...... 367 

345. Transverse and Longitudinal Sections of the Langen Mono-rail Carriages at Elberfeld . 368 

346. A Terminal Station of a Langen Mono-rail System ........ 368 

347. Langen Mono-rail Carriage for 85 Passengers, as proposed for Berlin. (Length between 

Buffers, 52 ft. 6 in.) ............. 369 

348. Designs of Langen Mono-rail System over a River . . .... 370 

349. Designs of Langen Mono-rail System over a Street ........ 370 

350. Supporting Structure for the Berlin Project for a Langen Mono-rail System (Scale, 1 : 50) 371 

351. Curves showing Variation of Weight Coefficient of Railway Motors, with Speed in 

Revolutions per Minute ............. 373 

352. Curves showing Variation of the Total Weight of Railway Motors, with Speed and 

Revolutions per Minute ............. 374 

353. Curve showing relation of Weight of Motor in Metric Tons to D^yg of Armature for 

Continuous Current Railway Motors .......... 376 

354. Curves showing Values of Gross Core Length of Armature for various Weights of Motors 

and Diameters of Driving Wheels. (See Table CXI.) ....... 377 

355. Curves for Gearless Motors, showing Overall Length of Motor Frame for various Motor 

Weights and Diameters of Driving Wheels. (See Table CXII.) ..... 379 

356. Curves for Geared Motors, showing Overall Length of Motor Frame for various Motor 

Weights and Diameters of Driving Wheels. (See Table CXIII.) ..... 380 

357. Curves showing Limiting Lowest Speeds of 75 h.-p., 150 h.-p., and 300 h.-p. Geared and 

Gearless Motors for various Diameters of Driving Wheels ...... 381 

xviii 




LIST OF ILLUSTRATIONS 


FIG. 

358. Limiting Values of Motor Speed (r.p.m.) for Different Train Speeds (Miles per Hour) for 

Motors of 75, 150, and 300 h.-p. . . . . . . . . . To face 

359. Curves showing Relation between Speed of Locomotive and Driving Wheel Diameter, 

Motor Speed, and Weight ............ 

360. Diagram of Repulsion Type Single-Phase Motor ........ 

361 Diagrams of the Latour-AVinter-Eichberg Type of Single-Phase Commutator Motor 

362. Compensated Series Type of Single-Phase Commutator Motor . . . . . 

363. Assembly of British Thomson-Houston Co.’s Compensated Series Single-Phase Railway 

Motor ................ 

364. Assembly of British Thomson-Houston Co.’s Compensated Series Single-Phase Railway 

Motor ................ 

365. Field for British Thomson-Houston Co.’s Compensated Series Single-Phase Railway 

Motor ................ 

366. Parts of British Thomson-Houston Co.’s Compensated Series Single-Phase Railway 

Motor ................ 

367. Assembly Drawing giving the Main Dimensions of British Thomson-Houston Co.’s 75 h.-p. 

Single-Phase Compensated Series Type Railway Motor ...... 

368. G.E.A. 605 Railway Motor. Characteristic Curves on 250-volt Alternating-Current 

Circuit, 25 Cycles. Efficiency corrected for a Copper Temperature of 75° Cent. 
33-inch Wheels 73/17 Gear. (British Thomson-Houston Co.) ..... 

369. G.E.A. 605 Railway Motor. Characteristic Curves on 250-volt Continuous-current 

Circuit. Efficiency Corrected for a Copper Temperature of 75° Cent. 33-inch Wheels 
73/17 Gear (British Thomson-Houston Co.) ......... 

370. Car Wiring for T—33 A. Controllers with Four G.E.A. 605 Compensated Motors for A.C. 

Operation (British Thomson-Houston Co.) ......... 

371. British Thomson-Houston Co.’s Latest Form of Oil-Cooled Compensator, as Employed in 

Single-Phase Railway System ........... 

372. Diagram of Connections of British Thomson-Houston Co.’s Single-Phase Railway System 

as arranged for the Multiple-Unit System of Control ....... 

373. Diagram of British Westinghouse Electric and Manufacturing Co.’s Single-Phase Series 

Motor, with Forced Neutralising Winding, and showing Normal Distribution of 
Magnetic Flux .............. 

374. Characteristic Curves of British Westinghouse Electric and Manufacturing Co.’s Standard 

Single-Phase Railway Motor ............ 

375. British Westinghouse Electric and Manufacturing Co.’s Single-Phase Motors and Control 

Equipment Connections for Working on Alternating-Current or Continuous-Current 
Circuits ................ 

376. British Westinghouse Electric and Manufacturing Co.’s Wiring Diagram for a Motor Coach 

equipped with Single-Phase Series Motors and Electro-Pneumatic Multiple-Unit Control 
System ................ 

377. Armature of British Westinghouse Electric and Manufacturing Co.’s 150 h.-p. Single- 

Phase Railway Motor ............. 

378. Outline Drawing of 150 h.-p. Single-Phase Series Wound Railway Motors, as manufactured 

by the British Westinghouse Electric and Manufacturing Co. . . . To face 

379. Field Frame of British Westinghouse Co.’s 150 h.-p. Single-Phase Railway Motor with the 

Neutralising Windings only in Place .......... 

380. Field Frame of British Westinghouse Co.’s 150 h.-p. Single-Phase Railway Motor with 

both the Neutralising Windings and the Magnetising Coils in Place .... 

381. Diagram, showing Relative Electrical Connections between Auto-Transformer and 

Preventive Coil and Voltages applied to Motors for the several Positions of Master 
Controller (British Westinghouse Electric and Manufacturing Co.) .... 

382. Diagram, showing Distribution of Current with Controller in Second Position (British 

Westinghouse Electric and Manufacturing Co.). 

383. Diagram, showing Distribution of Current with Controller in Transition from Second to 

Third Position (British Westinghouse Electric and Manufacturing Co.) 

384. Photograph of the High-tension End of an Air-Blast Type of Auto-Transformer, as 

employed in the British Westinghouse Co.’s Single-Phase Railway System . 

xix 


PAGE 

384 

387 

393 

394 
396 

396 

397 

397 

398 
398 

400 

401 

402 

402 

403 

403 

404 

405 

406 

407 

408 

408 

409 

409 

410 
410 
410 


LIST OF ILLUSTRATIONS 


FIG. 


385. Outline Drawing of Oil-insulated Auto-Transformer by the British Westinghouse 

Electric and Manufacturing Co. 

386. Electro-pneumatically-controlled Unit Switches, as employed in the British Westinghouse 

Co.’s Single-phase Railway System .......... 

387. British Westinghouse Co.’s Self-Reversing Pantograph Trolley .... 

388. British Westinghouse Co.’s Self-Reversing Pantograph Trolley ...... 

389. British Westinghouse Co.’s Exhibition Car at Trafford Park, Manchester . . . . 


390. Some Characteristic Curves of Single-Phase Commutator Motors (Full Line Curves) and 

Continuous Current Motors (Broken Line Curves) ...... To face 

391. Efficiency Curves of Latour-Winter-Eichberg Motor . 

392. Calculated Curve of 175 h.-p. Repulsion Motor at 1,500 Volts . 

393 and 394. Comparison of Efficiencies of Continuous-Current and Single-Phase Motors 

395. Diagram for Continuous-Current 2-mile Run .... 

396. Diagram for Single-Phase 2-mile Run ..... 

396a. Plan Outlines of Motor Carriages and Trailers ....... To face 

397. Paris-Metropolitan Motor Car with Rigid Wheel Base 

398. Truck of Paris-Metropolitan Motor Car with Rigid Wheel Base 

399. Goods Locomotive of North-Eastern Railway .... 

400. Mr. Worsdell’s Design for the Bogies for the Electric Motor Cars for the North-Eastern 

Railway. General Arrangement of Motor Truck (Brush Electrical Engineering Co., 
Ltd.) .............. To face 

401. Type of Bogie Truck as employed for Passenger Coaches on American Steam Railways 

402. General Arrangement of Motor Bogie in Hay’s Design for the Bogies for the Electric 

Motor Carriages of the Lancashire and Yorkshire Railway . . . .To face 

403. General Assembly of Motor Truck for the Motor Carriages of the Manhattan Elevated 

Railway ........... 

404. Truck for Central London Railway Geared Locomotive 
405 and 406. District Railway Trailer Trucks ..... 

407. District Railway Motor Car Truck ...... 

Central London Railway : General Arrangement of Motor Bogie 
Hedley’s Heavy Service Motor Truck used at Chicago 
Cast Steel Trailer Truck ........ 


408. 

409. 

410. 

411. 


412. 


To face 
To face 
To face 

Central London Railway: Cast Steel Trailer Bogies. General Arrangement of McGuire 

Truck . 

J. G. Brill Company No. 27 E Truck for Brooklyn Heights Elevated Railway. (May 22nd, 
1901) .............. To face 


413. Brill Truck. 

414. Brill Truck. 

415. Bogie Truck under Trailer End of Central London Railway Carriage 

416. Motor Truck showing Arrangement of Brakes on Manhattan Railway 
417 to 419. Standard Brake Heads and Shoes ...... 

420 and 421. Central London Railway : New Brake Block for Motor Trucks 

422. Central London Railway : Carriage Axle-Box ..... 

423. Master Car-builders’ Standard Axle-Box for a 4£" X 8" Journal 

424. Korbully Axle-Box ......... 

425 to 435. Car and Wagon Axles ....... 

436. Manhattan Wheel .......... 

437. Tyre Sections (issued 1904)......... 


To face 


To face 

To face 
To face 


PAGE 

412 

412 

413 

413 

414 

416 

417 

418 
422 
424 
424 
424 

430 

431 

432 


432 

433 

434 

436 

437 

438 

439 

440 
440 
440 

440 

440 

441 

442 
442 

447 

448 

449 

450 
454 
454 
458 
460 
462 


xx 




List of Tables 


PART i 

THE MECHANICS OF ELECTRIC TRACTION 

TABLE PAGE 

I. Values of V 3 .............. 5 

II. Rolling Stock Data ............. 14 

III. Equivalent Values of Distance, English and Metric ....... 18 

IV. Equi/alent Values of Speed, English and Metric ....... 19 

V. Comparative Table of Speeds ...... .... 19 

VI. Comparative Table of Speeds.20 

VII. Tractive Force and Accelerating Rate ......... 22 

VIII. Corresponding Schedule Speeds in Miles per Hour for Runs of following distances 

between Stops ............. 29 

IX. Consumption of Energy at Axles in Watt Hours per Ton Mile, one Stop per Mile . 48 

X. Average Power at Axles in Kilowatts per Ton, one Stop per Mile .... 44 

XI. For a Run of two Miles between Stops, at an average Speed of 80 Miles per Hour, 

this Table sets forth the Calculations of the Tractive Force (T. F.), Power and 
Energy at the Axles per Ton Weight of Train for a 200-Ton Train at various Rates 
of Acceleration, the Braking giving a Rate of Retardation equal to the Rate of 
Acceleration ...... ........ 45 

XII. Recoverable Energy per Ton Mile in Percentage of Total Energy expended at Axles 

per two Mile run from Start to Stop and Average Speed of 30 Miles per Hour . 46 

XIII. Summary of Results given in Table XII. ......... 47 

XIV. G.E. 66 A. Railway Motor at 500 Volts. Ratio of Gearing = 3 94. Diameter of 

Car Wheels = 34 ins. ............ 57 

XV. Four G.E. 66 A. Railway Motors. Ratio of Gearing = 3 - 94. Diameter of Car 

Wheels = 34 ins. All four Motors in Parallel ....... 59 

XVI. Four G.E. 66 A. Railway Motors. Ratio of Gearing = 3'94. Diameter of Car 

Wheels = 84 ins. All four Motors in Parallel ....... 60 

XVII. Controller positions for four G.E. 66 A. Motors. Mean Acceleration = 1 Mile per 

Hour per Second. Speed = 13’4 Miles per Hour ....... 65 

XVIII. Distance covered during each Operation for Run of one Mile ..... 67 

XIX. Nett Energy at Car Wheel. Mean Rate of Acceleration = one Mile per Hour per 

Second ............... 69 

XX. Comparison of five Alternative Methods of Motor Control ...... 75 

XXI. Calculations for a Half-mile Run at an Average Speed of 19 Miles per Hour. 120-Ton 

Train. Level Track ............ 77 

XXII. Comparison of Results of Half-mile Runs with various Periods of Coasting. Acce¬ 

leration = one Mile per Hour per Second in all cases. 120-Ton Train. Level 

Track. 79 

XXIII. Comparison of Results of Half-mile Runs at an average Speed of 19 Miles per Hour, 

and with various Periods of Coasting. 120-Ton Tram. Level Track. Varying 
Rates of Acceleration . . . . . . . . . . . .79 

XXIV. Calculations for Operation of a 120-Ton Train at an average Speed of 19 Miles per 

Hour over a Half-Mile Section with a 273 per cent, down Gradient for the first 
300 ft., and a 273 per cent, up Gradient for the last 300 ft. . . . • • 81 

XXV. Schedule of Gradients on the various Sections of the Railway ..... 84 

XXVI. Continuous Current Motor Equipments Employed on a Number of Typical Railways 88 


XXI 





LIST OF TABLES 


TABLE PAGE 


XXVII. Schedule Speed with 15 Second Stops, for a Mean Acceleration of 1*5 Miles per 
Hour Per Second, and a Mean Retardation of l - 5 Miles per Hour per Second, 
when the Maximum Speed does not exceed the Average Speed from Start to 

Stop by more than 33J per cent..91 

XXVIII. Armstrong’s Data for average Input to Train under various Conditions of Service . 91 

XXIX. Representative Data of Trains for various Services ....... 94 

XXX. Watt-Hours Input to Trains for various Services per Seat Mile .... 94 

XXXI. Watt-Hours Input to Trains for various Services per Seat Mile .... 94 

XXXII. Dependence of Energy Consumption on Schedule Speed ..... 95 

XXXIII. Comparison of Input per Seat Mile with Continuous Current and Single-Phase 

Equipments .............. 96 

XXXIV. Further Comparisons of Input with Continuous Current and Single-Phase Equip¬ 
ments ............... 96 

XXXV. Comparison of Schedule Speeds with Continuous Current and Single-Phase 

Equipments .............. 96 


PART II 

THE GENERATION AND TRANSMISSION OF THE ELECTRICAL ENERGY 


XXXVa. Schedule of Type and Capacity of Plant Installed at the Central London Railway 

Generating Station . . . . . . . . . • . .119 

XXXVb. Schedule of Type and Capacity of Plant Installed at the Generating Station of the 

Glasgow Corporation Tramways .......... 122 

XXXVc. Schedule of Type and Capacity of Plant Installed at the British Tramways Gene¬ 
rating Station ............. 126 

XXXVd. Schedule of Type and Capacity of Plant Installed at the Generating Station of the 

Dublin United Tramways Co. .......... 130 

XXXVI. Operating Costs of Electrical Power Generating Stations ..... 133 

XXXVII. Annual Overall Efficiencies of Three Electrical Power Generating Stations . . 134 

XXXVIII. Annual Overall Efficiencies of Twenty-six Electrical Generating Stations . . 136 

XXXIX. Annual Overall Efficiencies of English and Foreign Electrical Generating Stations . 134 

XL. Table of Thermal Efficiency of Engine and Generator and Overall Efficiency of 

Complete Plant on Steady Load .......... 138 

XLI. Table of Overall Efficiencies of Steam Plants under Service Conditions . . . 139 

XLII. Data of Cables for Various Voltages ....... To face 142 

XLIII. British Standard Sizes of Stranded Conductors for Electric Supply . . . 147 

XLIV. Maximum Permissible Current in Copper Conductors according to the Rules of the 

Institution of Electrical Engineers ......... 148 

XLV. Current Densities in Copper Wires Employed in Cables for 1,000 Volts and over, 

according to the Rules of the German Society of Electricians .... 149 

XLVI. Particulars of Central London Railway High Tension Cables ..... 157 

XLVII. Dielectric Capacity of Central London Railway Cables ....... 158 

XLVIII. Weights and Dimensions of Central London Railway High Tension Cables . . 158 

XLIX. Particulars of London Underground Railways High Tension Cables . . . 159 

L. Engineering Standards Committee’s Table of Thicknesses of Insulation for Paper- 

Insulated Concentric Cables for Pressures exceeding 2,200 Volts . . . 162 

LI. Engineering Standards Committee’s Table of Thicknesses of Insulation for Paper- 

Insulated Three-Core Cables for Pressures exceeding 2,200 Volts . . . 163 

LII. Engineering Standards Committee’s Table of Thicknesses of Insulation for Rubber- 

Insulated Concentric Underground Cables for Pressures exceeding 660 Volts . 163 

LIII. Engineering Standards Committee’s Table of Thicknesses of Insulation for Rubber- 

Insulated Three-Core Underground Cables for Pressures exceeding 660 Volts . 164 

LIV. Resistances and Weights of Copper Conductors of various Sizes .... 167 

LV. Inductances and Reactances of Copper Conductors.. 167 

xxii 



LIST OF TABLES 


TA BLE PAGE 

LYI. Capacities and Charging Currents of Copper Conductors ..... 168 

LVII. Data of 600-K.W. Rotary Converter.177 

L\ III. Amperes Input to Rotary Converter with Varying Field Excitation, at Full Load 

Output .............. 178 

LIX. Amperes Input to Rotary Converter with Varying Field Excitation for various 

Outputs . . . . . . . . . . . . . .179 

LX. Adjustment with 64 per cent. Compounding at Full Load, and for Unity Power 

Factor at 75 per cent, of Full Load.179 

LXI. Rotary Converter adjusted for Unity Power Factor at Three-quarter Load and 

64 per cent. Compounding at Full Load.180 

LXII. Variation in Rotary Converter Voltage with Varying Load ..... 182 

LXIII. 64 per cent. Compounding at Full Load, Adjustment for Unity Pow'er Factor at 

Three-quarter Load ............ 182 

LXIV. Rotary Converter adjusted for Unity Power Factor at Three-quarter Load and 

36 per cent. Compounding at Full Load ........ 183 

LXV. 36 per cent. Compounding at Full Load, Adjustment for Unity Power Factor 

at Three-quarter Load ............ 184 

LXVI. Rotary Converter with Shunt Excitation.185 

LXVII. Shunt Excitation and a Resistance of 0 02 Ohm per Phase ..... 185 

LXVIII. Some Data of a Rotary Converter Installation ....... 188 

LXIX. Distribution of Current in Rotary Converter and Battery for a Period of Five 

Minutes .............. 197 

LXIXa. Cost of Battery-Booster Sets, including the Battery and Booster and Switch Gear 
complete and ready for work, but excluding the Battery House—One-liour 
Discharge Rate . . . . . . . . . . . . 202 

LXIXb. Cost of Battery-Booster Sets, including the Battery and Booster and Switch Gear 
complete and ready for work, hut excluding the cost of the Battery House— 
Three-hours Discharge Rate .......... 203 

LXX. Number of Sub-stations on various Electric Railways and their Capacity . . 209 

LXXI. List of Sub-stations on various Electric Railways and Data regarding their 

Equipment .............. 209 

LXXII. Floor Space of various Electric Sub-stations . 211 

LXXIII. Composition and Conductivity of Conductor Rails ....... 248 

LXXIIIa. Showing Spacing of Insulating Supports ....... . 249 

LXXIV. Particulars of Conductor Rails for various Railways ..... 249 

LXXV. Particulars of Conductor Rails for various Railways . ... 256 

LXXVI. Table of Span and Dip of Suspension Cables ........ 260 

LXXVII. Particulars of Standard Track Rails .... ... 272 

LXXVIII. Particulars of Track Rails of various Railways ... 272 

LXXIX. Resistances of Rail Bonds ........... 279 

LXXX. Comparison of Resistances of various Rail Bonds, not including in any case the 

Resistance of the Rail . . . . . . . . . . . .279 

LXXXI. Particulars of Rail Bonds on various Railways . . . ... . . 280 

LXXXII. Resistance, Reactance and Impedance per mile of Bull Head Rails. Standard 

Section, 25 cycles per second.282 

LXXXIII. Resistance, Reactance and Impedance per mile of Bull Head Rails. Standard 

Section, 20 cycles per second .......... 282 

LXXXIV. Resistance, Reactance and Impedance per mile of Bull Headed Steel Rails. 

Standard Section, 15 cycles per second ........ 283 

LXXXV. Impedance of Rail portion of Circuit ......... 283 

LXXXVI. Impedance of Overhead Conductor .......... 284 

LXXXVII. Total Impedance per Mile of Circuit ......... 285 

LXXXVIII. Table of Current Values in Track Rails for 10 Volts Difference of Potential 

between ends of Rail for 100 lb. Rail ......... 286 

LXXXIX. Table of Pressure Differences on Track Rails with 100 Amperes in Rail—100 lb. 

Rail ............... 287 

xxiii 




LIST OF TABLES 


PAET III 

THE ROLLING STOCK 

TABLE PAGE 

XC. Leading Data of New York Central Electric Locomotive ..... 293 

XCI. Weight of Electrical Equipment of New York Central Locomotive . 293 

XCII. Composition of Trains in New York Central Tests of April, 1905 303 

XCIII. Average Yoltage at Live Rail during Acceleration ...... 303 

XCIV. Comparison of Steam and Electric Locomotives on New York Central Railway . 305 

XCV. Leading Data of Baltimore and Ohio 1896 Gearless Locomotive .... 308 

XCYI. Principal Dimensions of Baltimore and Ohio 1903 Geared Two-unit Locomotive 313 
XCYII. Weight of Electrical Equipment of Baltimore and Ohio 1903 Geared Two-unit 

Locomotive ............. 314 

XCV1II. Detailed Weights of Gearless Central London Railway Locomotive . . . 317 

XCIX. Gearless Central London Locomotive Weights, Exclusive of Electrical Equip¬ 
ment .............. 319 

C. Weights of Electrical Equipment of Gearless Central London Locomotive . . 319 

Cl. Principal Data of Paris-Orleans Geared Electric Locomotives .... 321 

CII. Weights of Electrical Equipment of Paris-Orleans Geared Electric Locomotives 323 
CIII. Data of Paris-Orleans Rolling Stock ......... 324 

CIY. Comparison of Steam Locomotive with Gearless Bi-polar Electric Locomotive . 325 

CV. Itemised Weights of Oerlikon 15,000-volt Fifteen-cycle Locomotive, with Single- 

Phase Commutator Motors .......... 348 

CVI. Principal Data of a Carriage of the Langen Mono-rail System .... 371 

CVII. Weight Coefficients of Continuous Current Railway Motors .... 374 

CVIII. Total Weights of Continuous Current Railway Motors, exclusive of Gearing . 374 

CIX. Valatin’s Data for Railway Motors ......... 375 

CX. Values of D 2 Ay for Continuous Current Railway Motors ..... 376 

CXI. Gross Length of Core in Centimetres (a g) of Motors of various Weights, for 
Driving Wheels of various Diameters, taking D = 0'5 x Diameter of Driving 

Wheel.377 

CXIL Overall Length of Frame, in Inches, of Gearless Motors of various Weights for 

Driving Wheels of various Diameters ........ 378 

CXIII. Overall Length of Frame, in Inches, of Geared Motors of various Weights for 

Driving Wheels of various Diameters ........ 379 

CXIY. Speeds of 75 h.-p. Motor for various Locomotive Speeds in Miles per Hour and 

various Driving Wheel Diameters ......... 382 

CXV. Speeds of 150 h.-p. Motor for various Locomotive Speeds in Miles per Hour and 

various Driving Wheel Diameters ......... 383 

CXVI. Speeds of 300 h.-p. Motor for various Locomotive Speeds in Miles per Hour and 

various Driving Wheel Diameters ......... 384 

CXVII. Showing Particulars of Motors for the Mean Points in Fig. 358 .... 385 

CXVIII. Data for Weights of Locomotives and Motor Equipments ..... 386 

CXIX. Weight of Single-Phase and Continuous Current Motors ..... 389 

CXX. Showing the Seating Capacity per Square Foot of Coaches used on various 

Railways .............. 429 

CXXI. Journal Pressures ............ 458 

CXXII. Various Qualities of Steel for Axles ......... 460 

CXXII1. Qualities of Steel for Tyres ........... 463 


xxiv 




Part I 

THE MECHANICS OF ELECTRIC TRACTION 


B 


















































ELECTRIC RAILWAY ENGINEERING 


Chapter I 

TRACTIVE RESISTANCE AT CONSTANT SPEED 

T HERE is a general impression that the subject of tractive resistance on rails 
is but little understood. Although this is to a certain extent the case so far 
as relates to an analysis of the various physical causes of resistance to motion on 
rails, there is now fairly general agreement as to the amount of the total tractive 
resistance at various constant speeds on a modern well-built surface railway on a calm 
day on a straight track. While there are minds to which an indefiniteness of the 
nature of 30 per cent, presents itself as a hopeless impediment, there appears to 
be no justification for this attitude so far as relates to tractive resistance on rails. 
It is true that the degree of wetness or dryness of the rail, the velocity of the wind, 
the contour of the train and its mechanical design, and the character of the 
permanent way, all introduce considerable variations. The engineer will not 
disregard these influences; indeed, each of these influences will, in a given case, 
require careful study. But, so far as relates to preliminary estimates of the 
average power required at the axles, the most elaborate recent experimental data 
obtained in different countries and under varied conditions, converge toward 
sufficiently definite values. 

As a matter of fact, even were the latest experimental data for tractive resistance 
at various constant speeds widely divergent, no considerable uncertainty would be 
introduced into the results, except for the case of long runs between stops. For runs 
of lengths up to a mile or two at high schedule speeds, the energy consumed during 
the accelerating interval is so considerable a percentage of the total energy 
consumption, as to mask very great inaccuracies in the data of tractive resistance 
at constant speed. The calculation of the energy consumed during the accelerating 
interval is much more independent of assumptions based on experimental data. 
The shorter the run between stops, the greater is the importance of accuracy in 
estimations affecting the acceleration values, while the estimations of the frictional 
resistance are of comparatively little account. The longer the run between 
stops the more important does it become to base the estimations upon fairly 
correct data of tractive resistance. 


3 


}} 2 



ELECTRIC RAILWAY ENGINEERING 


Tractive Resistance at Starting. 

The tractive resistance at starting on a level is very dependent upon the type 
and design of the bearings, the wheel diameter, and the design and condition of 
the permanent way. Aspinall’s value of 17 lbs. per ton is a fair 
average figure for the best conditions obtaining on main lines with medium and 
heavy trains. On the Central London Tube Railway the starting resistance on 
the level is 20 lbs. per ton for a 113-ton train comprising seven cars. On 
the City and South London Tube Railway, McMahon’s experiments showed on 
occasions a starting resistance of 40 lbs. per ton for 26-ton trains. 1 This value 
is rarely exceeded, even on urban tramway lines. 

Tractive Resistance at Constant Speed. 

For very low speed, the tractive resistance decreases with increasing speed, 
reaching a minimum at some 5 miles per hour. The speed corresponding to 



5peed m Mi lee p>er Hour 

Fig. 1. Curves of Tractive Resistance at Low Speeds for an 
83-Ton 75-Foot Car, as deduced from the Berlin-Zossen Tests. 


the minimum tractive resistance is, however, a very variable quantity, and is very 
dependent upon the construction and condition of the permanent way and of the 
rolling stock. For good conditions, the minimum tractive resistance may be as 
low as 3 lbs. per ton. In the case of the 83-ton cars employed for the 

1 “ The curve showed the variation in the draw-bar pull, its high value at the start, about 40 lbs. 
per ton, dropping to the minimum of 9 lbs. per ton. . . . The most striking feature of it, was the high 
resistance at starting, and, in order to test that, an experiment had been made with the train in a 
siding, a spring balance being used to start it very slowly; the resistance in that case had been found 
to be 20 lbs. to 25 lbs. per ton. A similar experiment on a locomotive had shown the resistance to 
be 25 lbs. to 30 lbs. per ton, but the first test when the locomotive was standing had always given a 
higher result, and that seemed to be due to the squeezing out of the oil.”—McMahon, “ Proceedings 
of the Institution of Civil Engineers” (1901), Yol. CXLYII., p. 213. 

Moreover, McMahon’s wheel diameters were but 24 ins. For McMahon’s results, see also 
Curve A of Fig. 6, on p. 9. 


4 




































TRACTIVE RESISTANCE AT CONSTANT SPEED 


Berlin-Zossen tests, the minimum resistance amounted to a little less than 3 lbs. 
per ton, as may be seen from the curve of Fig. 1, relating to the results 
obtained at low speeds. The two cars with which most of the tests were made, 
weighed 90 tons (A.E.G. Car) and 77 tons (S. and H. Car) respectively. For our 
purposes the mean value of 83 tons is taken. 

For electric traction, however, but little interest attaches to the tractive resistance 
at speeds of less than 10 miles per hour. From 10 miles to 100 miles per hour 
the following formula, due to Aspinall, leads to very trustworthy results:— 

V* 

11 = 2 5 + 51 + 0*028 L. 

R = tractive resistance in pounds per (metric) ton (of 2,200 lbs. or 1,000 kgs.). 

Y = speed in miles per hour. 

L = length of train in feet. 

The formula, owing to the fractional exponential power of V, is an inconvenient 

5 

one to use, and hence Table I. has been prepared, in which values of V :J are given. 


Table I. —Values of V 3 . 


V 

Speed in Miles 
per Hour. 

vl 

10 

46-8 

15 

91-5 

20 

151 

25 

214 

30 

295 

40 

473 

50 

676 

60 

933 

70 

1,180 

80 

1,510 

90 

1,820 

100 

2,160 

120 

2,820 


The curves of Fig. 2 have been plotted, by means of Aspinall’s formula, for 
train lengths of 100, 1,000, and 2,000 ft., which cover most cases which will occur in 
heavy electric traction. 1 

Now while it is quite true that these results vary from the results of other careful 
investigations, sometimes by high percentages, this is really of minor importance, on 
account of numerous other uncontrollable factors. Thus in a heavy wind the train resist¬ 
ance will often be doubled. Variations in the type and condition of the rail, 2 the condition 

1 “ On the New York Central and Hudson River Railroad there were several trains daily of 
3,000 tons to 4,000 tons, drawn by American locomotives, the number of cars ranging from 
seventy-five to ninety.”—Dudley, “Proceedings of the Institution of Civil Engineers’ (1901), 
Vol. CXLVIL, p. 261. 

2 “ Dr. P. H. Dudley has stated that when he substituted an 80-lb. rail for a worn 65-lb. rail 
it made a difference of 75 h.-p. to 100 h.-p., and he estimated that a 105-lb. rail saved 200 h.-p. as 

5 








ELECTRIC RAILWAY ENGINEERING 


of permanent way, type of rolling stock, etc., also introduce great differences in the 
train resistance, as also the location of the driving power, whether distributed upon 
the axles of the different vehicles, or concentrated on a locomotive. These and similar 
considerations lead to the conclusion that the results set forth in the curves of Fig. 2 
are amply precise as a mean basis for calculations. 

The recent high-speed tests at Zossen, near Berlin, included elaborate 



Fig. 2. Curves of Tractive Resistance for Various Lengths of Train. 


determinations of the tractive resistance. These tests were made upon single coaches 
of a length of 75 ft. and weighing 83 tons, 1 the design, chiefly on account 

compared with the 60-lb. or 65-lb. rail.”—Aspinall, “ Proceedings of the Institution of Civil 
Engineers ” (1901), Vol. CXLVII., p. 241. 

Dr. Dudley did not state the total horse-power, which, of course, would have to be known 
in order to lend definiteness to his data. 

1 Camp (“ Notes on Track,” 2nd edition, 1904) gives the following concise resume of some of 
the leading conditions of the Berlin-Zossen tests :—“ During the fall of 1903 some unprecedented 
speeds were made on the Marienfelde-Zossen military line in Germany, which aroused a world-wide 
sensation, and the particulars of the track construction and of the rolling stock are interesting in the 
present connection. The road was 14f miles long, nearly level, and mostly straight, there being one 
curve of 52| minutes (radius 6,562 ft.) near one end. The track was laid with 84i-lb. rails, generally 
39 - 4 ft. long, on fir ties, eighteen to the rail length, with tie plates, six-bolt angle-bar splices 31| ins. 
long, with vertical flanges hanging li ins. below base of rail, between joint ties, but some of the 
joints were of the lap type. The ballast was broken stone. On 10i miles of the line, guard rails 
were laid inside the traffic rails to a flangeway of l - 97 ins. These were ordinary T-rails laid on 
side, with the base (4g ins. wide) presented for the service side of the guard, the upper edge coming 
If ins. above the top of the traction rail. They were supported upon cast-iron chairs, lag-screwed 
to the ties. With the exception of these guard rails on part of the line (which were found to be an 

6 













































































TRACTIVE RESISTANCE AT CONSTANT SPEED 


of the great capacity of the motor equipment, thus having the exceptional constant 
of IT tons weight per foot of overall length. 1 The results obtained from these 
tests are given in the lower curve of Fig. 3, and the results calculated from 
Aspinall’s formula are given in the upper curve of the same figure. The agreement 
is seen to be very good. But for this excellent agreement between the Aspinall and 
the Zossen tests, both of which were most elaborate, the values at the lower speeds 
would have been pronounced decidedly too low, as all prior formulae gave higher 



results at low speeds. That this is the case is evident from Figs. 4 and 5, taken from 
Gottshall’s “Electric Railway Economics” (pp. 156 and 154). 

unnecessary precaution), the track was, as thus to be seen, only of ordinary construction. There 
were two electric cars, one being used in each of the many experiments. Each car was 72 ft. long, 
mounted on two six-wheel trucks, wheels 49'2 ins. diameter; wheel base of truck 16 - 4 ft. long ; each 
truck equipped with two 250-h.-p. motors on the outside axles, and air brakes, with brake shoes on 
both sides of all wheels ; total weight of car, 92 tons. As the experiments continued, the speeds 
were gradually increased until trips were made repeatedly at 105 to 110 miles per hour, or the whole 
distance each way in eight minutes. The energy consumed in driving the car at such speeds was 
about 1,600 h.-p., and stops were made in 6,560 feet from the point where brakes were applied. 
On October 23rd one of the cars attained a speed of 1284 miles per hour, and on October 28th the 
other car was run at the tremendous speed of 1304 miles per hour.” 

In the above quotation the weights in tons have been changed by the writers from the American 
short ton of 2,000 lbs. employed by Camp, to the metric ton of 2,200 lbs. Camp’s weight per car 
evidently relates to the A.E.G. car. 

1 In present practice on steam and electric railways, the weight of loaded car or train pei foot 
of overall length, rarely exceeds 0 - 65 tons, and as a rough but representative value 0 5 tons pei foot 
of overall length may be taken. (See also Table II., on p. 14.) 

7 































































ELECTRIC RAILWAY ENGINEERING 

In tube railways, where there is small clearance between the walls and the tiain, 
high-tractive resistance (depending partly on the amount of clearance) has been found, 
and, of course, varying as a function of the speed. In Fig. G the full line curves 
(b and c) are deduced from tests on the Central London Railway (in which the 
tube’s internal diameter is 11 ft. 6 ins.), showing the train resistance as a function of 
the speed. The minimum clearance between the tube and train is 6 ins. 

From measurements made on the City and South London Railway, McMahon 
obtained the data from which the broken line curve (a) of Fig. G has been deduced. 



Fig. 4. Curves for Tractive Resistance according to well-known Formula. 

o 

Single-Car Operation. Weight of Car about 22 Tons. 

From the train test curves obtained on the Central London Railway, the total 
tractive resistance at 30 miles an hour is 1,200 lbs. for a seven-car train, and 600 lbs. 
for a single car, the weights of the trains being 125 tons and 25 tons respectively. 
It appears that there is a constant figure of 6 lbs. per ton for journal friction, etc., and 
a figure for the head and tail resistance which depends upon the speed and is unaftected 
by the length of the train, the actual equation for the total tractive resistance being— 

V 2 

Resistance in pounds per ton = 6 -R 0*5 ^> 

where V is the speed in miles per hour and W is the weight of the train in metric tons. 

8 
























































































TRACTIVE RESISTANCE AT CONSTANT SPEED 

In Fig. 7 are two curves, one showing the resistance in pounds per ton for a seven- 
car Central London train, as worked out by the above formula, and the other showing 
the resistance of this train on a surface track, as worked out by Aspinall’s formula. 



Fig. 5. Same as Fig. 4, but for Train of Five 40-Ton Carriages, say 200 Tons. 


No tests have been made with high-speed service in such tube railways, but the 
resistance can be reasonably expected to be considerably increased at speeds above, 
say, 40 miles per hour. Thus from the Zossen tests on an 83-ton car it 



Syof ec/ m f'rfi/es f>er Hour- 

Fig. 6. Curves of Tractive Resistance in Tube Railways. 

9 


H 2 


<o 

£ 


O 

T: 



















































































































































ELECTRIC RAILWAY ENGINEERING 


has been found that at a speed of 40 miles per hour the air resistance becomes 
equal to the mechanical resistance, and at a speed of 100 miles per hour the 
air resistance on surface roads is four times the mechanical resistance. This is seen 
from the curves of Fig. 8, in which the curve of total resistance for the Zossen tests 
is supplemented by two curves of the component resistances due respectively to air 
resistance and mechanical resistance. The longer the train, however, the less is the 
percentage which the air resistance constitutes of the total resistance ; and for well- 
vestibuled trains of several hundred tons weight, the air resistance would probably 
not exceed the mechanical resistance below speeds of from 45 to 50 miles per hour. 
For a five-coach train, Aspinall (“Proceedings of the Institution of Civil Engineers,’' 
(1901), Yol. CXLVIL, p. 249) estimates the atmospheric resistance as becoming equal 



Fig. 7. Curves of Tractive Resistance in Tube Railways and on Surface. 


to 50 per cent, of the total resistance at 80 miles per hour. But all his statements 
relate to the train behind the engine, and the engine shields the train from a 
considerable portion of the air resistance. Thus for a motor-car train, the air resist¬ 
ance would become equal to the mechanical resistances at a much lower speed, and 
the corresponding speed would be lofrer the shorter the train. 

From such results it is evident that for high-speed work it would be futile to 
attempt to materially reduce the train resistance by modifications in the design of the 
rolling stock and permanent way, 1 and that attention should rather be directed to the 
contour of the train. Not only does the form of the front and rear ends greatly affect 

1 Of course the greatest attention must, nevertheless, be given to the design of the rolling stock 
and permanent way, in order to render high speeds practicable and satisfactory, and to exempt 
these parts from rapid deterioration; but so far as relates to obtaining the most economical result 
for tractive effort in pounds per ton at high speeds the chief attention should be given to the contour 
of the individual carriages and of the train as a whole. Improved bearings will not affect the air 
resistance. 

IO 









































































TRACTIVE RESISTANCE AT CONSTANT SPEED 


the air resistance, but when a train is composed of many vehicles, it must, so far as 
practicable, present continuous unbroken surfaces from end to end. 1 

Curves materially increase the train resistance, not only at low, but at high, 
speeds. At moderate speeds, measurements have often shown 100 per cent, increase 
in the train resistance, even on well-designed curves of fairly large radius. 2 


Fig. 8. Curves of Component and Resultant Tractive Resistance for 
83-Ton 75-Foot Car, deduced from Berlin-Zosskn Tests. 



Heavily loaded trains have a resistance considerably lower (as expressed in 
pounds per ton) than light trains. 3 This consideration is of importance chiefly in 

1 “ ... At high speeds the air resistance is by far the most important factor, and that the 
proper shape of the car has to be very carefully determined.”—Siemens, “ Proceedings of the 
Institution of Electrical Engineers ” (May 26th, 1904). 

“ Attention must also be paid to those details of design which will reduce the train resistance, 
and more especially that element thereof known as ‘ wind resistance ,’ which is by far the greatest 
component of train resistance. Smooth, flat sides, with the platform ends rounded or tapered, 
and enclosed, are among the simple and effective methods employed. It is astonishing what a saving 
in watt-hours per ton mile, or per car mile, the application of the simple methods above suggested 
will produce, as indicated by recent tests.”—Gottshall, “ Electric Railway Economics,” p. 152. 

2 “An attempt had also been made to determine the effect of curves on the tractive resistance, but 
it had been found to be very difficult to do so on account of the curves on the line being so short. The 
results of three tests on a curve having a radius of 390 ft. gave 27'9 lbs. per ton at 16 - 5 miles per hour, 
whereas on the straight road the result was 12J lbs. per ton, leaving about 15 lbs. per ton due to the 
curve alone. Six experiments had been made on a curve of 540 ft. radius, giving 22 - 6 lbs. per ton at 
13| miles per hour, whereas on the level it was 1P3 lbs. per ton, leaving 1P3 lbs. per ton due to the 
curve.”—McMahon, “Proceedings of the Institution of Civil Engineers” (1901;, Yol. CXLYII., p. 215. 

3 “ With a train of empty wagons 1,830 ft. long, the resistance had been found to be 18 - 3 lbs. 
per ton at a speed of 26 miles per hour; a train of full wagons 1,045 ft. long had given 9'1 lbs. per 
ton at 29 miles per hour, and another of the same length, as low a figure as 6 - 2 lbs. per ton at 
28 miles per hour. He trusted, however, that these figures would not be regarded as results which 
could be finally established without further proof.”—Aspinall, “Proceedings of the Institution of 
Civil Engineers ” (1901), Yol. CXLYII., p. 197. 

















































































ELECTRIC RAILWAY ENGINEERING 


freight service, since in passenger service the weight of the passengers is but an 
inconsiderable percentage of the weight of the train in which they travel; he., whereas 
the goods transported constitute the greater part of the weight of the train in freight 
service, the passengers transported, including their luggage, rarely constitute much 
more than 10 per cent, of the total weight of the train. In a “ sleeper ” the occupants 
constitute less than 2*2 per cent, of the total weight hauled. 

From the statement that heavily loaded trains have a resistance considerably 
lower as expressed in pounds per ton (i.e., a lower “specific resistance”) than light 
trains, it might naturally be concluded that locomotives, which have a far higher 
weight in proportion to their length than the carriages they haul, would require a less 
tractive effort per ton of weight for a given speed. This is, however, not the case. 
Although in steam practice, with a passenger train having a total weight of 300 tons, 
the locomotive would weigh but 75 to 100 tons, or 25 per cent, to 33 per cent, of the 
total weight, from 35 per cent, to 55 per cent, of the power indicated by the 



Fig. 9. Percentage of Passenger AYeight to Total Train AA 7 eight 
(Grand Central Station to Mott Haven Junction). 


locomotive would be employed in the losses in the locomotive and in the power 
required to propel it, thus leaving but from 45 per cent, to 65 per cent, of the 
indicated power available for propelling the rest of the train. 1 Incidentally this 

1 “ In order to see how much power the locomotive absorbed as compared with the train, a 
certain number of experiments had been tried on the Lancashire and Yorkshire Railway, and it had 
been found that- the ten-wheeled engine (No. 1,392) absorbed 34 per cent, of the total horse-power. 
Mr. AV. M. Smith (‘ Proceedings of the Institution of Mechanical Engineers,’ 1898, p. 605) had 
given the results of his experiments as about 36 per cent, of the total horse-power; and Mr. Druitt 
Halpin had stated (‘ Proceedings of the Institution of Mechanical Engineers,’ 1889, p. 150) that the 
Eastern Railway of France had found that the engine absorbed 57 per cent, of the total horse-power 
developed ; while Dr. P. H. Dudley gave it at 55'6 per cent., and Mr. Barbier at 48 per cent. 
Probably 34 per cent, or 36 per cent, was about the right percentage, the other figures being much 
too high; at any rate, the experiments referred to in the paper rather pointed to that conclusion, 
though, of course, the actual figure depended on the load behind the engine.”—Aspinall, 
“ Proceedings of the Institution of Civil Engineers ” (1901), Yol. CXLVII., p. 197. 

12 
































































TRACTIVE RESISTANCE AT CONSTANT SPEED 

is an important fact to keep in mind in comparing the relative merits of traction 
by steam and electricity. In short trains, the percentage of the energy employed for 
the locomotive itself, is still higher. 

As an interesting instance of the small percentage which the live load constitutes 
in through and in suburban service respectively, there are given in Fig. 9, some 
curves applying to the conditions on the section of the New York Central and Hudson 
River Railway between the Grand Central Station in New York City and Mott Haven 
Junction. These curves are taken from a paper by Arnold published on p. 876 of 
Yol. XIX. of the “Transactions of the American Institute of Electrical Engineers.” 1 

A sleeper weighs some 3^ tons per passenger when carrying its full complement 
of passengers. In this case, the passenger represents less than 2 per cent, of the 
total weight hauled. Ashe and Keiley refer to this matter as follows:— 

“In all classes of electric cars the dead weight of car varies from about 
70 per cent, to 90 per cent, of the told weight plus the weight of seated passengers, 
and the power required for the operation of a given service varies directly as the 
weight of the cars moved. It is evident that the cost of the power plant and 
transmission system would be approximately proportional to the weight of the cars 
if electric heaters were not used. 

“ The ratio between dead weight and told weight of cars varies between wide 
limits; and on account of the indefinite character of the load, due to standing 
passengers, it would be difficult to give even approximate figures. However, a rough 
general statement of the amount of dead weight of car per seated passenger would 
be as follows:—Closed trolley car, longitudinal seats, 600 to 700 lbs. per seated 
passenger ; open trolley car, full cross seats, 400 to 500 lbs. per seated passenger; 
and suburban closed car, cross seats, and centre aisle, 1,000 to 1,200 lbs. per 
seated passenger.”—“Electric Railways,” Ashe and Keiley, pp. 171—172 ^London, 
Constable & Co., 1905). 

The direction and intensity of the wind may considerably increase or decrease the 
tractive effort required of the steam locomotive or of the electric motors, and this 
again is considerably dependent upon the design of the train as regards the contour 
of the front and rear ends, the vestibuling, and other details. Curves also exert a great 
influence, which is, however, difficult to predetermine. 2 The influence of gradients is 
readily determined by the principles of ordinary mechanics, and is equivalent to a 
positive or negative tractive effort of 22 lbs. per ton for a 1 per cent, gradient. 

While all these points require attention in specific cases, one must have some simple 
basis for the further preliminary study of the mechanics of heavy electric traction. The 
curves of Fig. 2, on p. 6, will be taken as the ultimate basis for this preliminary study. 

Although the length of the train and the weight in tons per foot of overall length, 
constitute the most correct basis for final reference, it is much more useful, even at 
some slight sacrifice of accuracy, to derive curves in which the length of the train in 
feet is replaced by the weight of the train in tons. For this purpose we must obtain 
representative figures for the weights of heavy single cars and of trains, per foot of 
overall length. A number of such figures have been compiled in Table II. 

1 “ It has been pointed out that only from 15 to 20 per cent, of a fully loaded train consists of a 
paying load, and with an average load as carried throughout the day, this percentage will be reduced 
to 10 per cent, or less—that is, nine-tenths of the energy consumed in moving this train at a 
constant speed is wasted.”—Armstrong, “ Transactions of the American Institution of Electrical 
Engineers ” (1898), Yol. XV., p. 375. 

2 For the tractive resistance on curves, see also the footnote on p. 11. 

13 


ELECTRIC RAILWAY ENGINEERING 


Table II. — Rolling Stock Data. 



Number 
of Seats. 

Overall 
Length 
in Feet. 

Loaded 
Weight in 
Metric: 
Tons. 

Loaded 
Weight in 
Metric Tons 
per Foot 
of Overall 
Length. 

Seats per 
Foot. 

Seats per 
Metric Ton 
of Loaded 
Weight. 

Steam railroad standard suburban train, made 
up of seven eight-wheeled coaches and 
locomotive ....... 

520 

389 

240 

0-62 

1-33 

2-16 

Great Northern and City continuous-current 
motor-car train, seven cars .... 

422 

355 

195 

0-55 

1-19 

2-16 

Mersey Railway continuous-current motor¬ 
car train ....... 

292 

300 

138 

0-46 

0-97 

2-10 

Manhattan Elevated standard continuous-cur¬ 
rent train, made up of four motor-cars and 
two trailer cars ...... 

286 

282 

125 

0-44 

1-01 

2-29 

Standard City and South London continuous- 
current four-car train, with locomotive 

128 

141 

41 

0-35 

0-91 

3-12 

Zossen car (S. and H.) ..... 

48 

76 

77 

•1-01 

0-63 

0-62 

Zossen car (A.E.G.) ..... 

48 

72 

93 

1-29 

0-66 

0-52 

Interborough Railway Co. fireproof car (Ashe 
and Iveiley, “ Electric Railways,” p. 178) . 

52 

52 

27 

0-52 

1-0 

1-9 

Burgdorf-Thun three-phase motor car . 

66 

49 

36 

0-74 

1-35 

1-83 

Chicago and Joliet inter-urban continuous- 
current motor car ..... 


36 

23 

0-64 



Closed trolley car with longitudinal seats 
(Ashe and Keiley, “ Electric Railways,” 

p. 172). 






31 to 2-6 

Open trolley car with full cross seats, as 
employed in summer in America (Ashe and 
Keiley, “ Electric Railways,” p. 172) . 






4-7to3-7 

Suburban closed car with cross seats and 
centre aisle (Ashe and Keiley, “ Electric 
Railways,” p. 172) 






2-0 to 1-6 

Liverpool Overhead Railway .... 

57 

45 

38 

6-845 

1-27 

1-5 

Metropolitan Elevated Railway (Chicago), 
west side ....... 

40 

40 



1-00 


Lecco Sondrio Railway (Ganz system), Val- 
tellina........ 

56 

57 

56-5 

0-99 

1-02 

1-01 

Indianapolis and Cincinnati Traction Co., 
single phase inter-urban car 

54 

55 

46-5 

0-85 

1-02 

1-16 

Data given by Armstrong, Street Railway 
Journal, Yol. XXVI., p. 1068, double truck car 

64 

60 

26 

0-43 

1-07 

2-46 

Ditto, double truck car ..... 

52 

50 

18-6 

0-37 

1-04 

2-8 

Ditto, double truck car ..... 

42 

40 

13 

0-33 

1-05 

3-22 

Ditto, single truck ...... 

26 

26 

6-8 

0-26 

1-00 

3-8 

Central London continuous-current seven-car 
train ........ 

324 

330 

133-5 

0-41 

0-98 

2-42 

Central London motor coach .... 

40 

46 

27-5 

0-50 

1-15 

1-45 

Central London trailer coach .... 

48 

46 

16-4 

0-28 

0-96 

2-82 

Metropolitan Railway (London) six-car train . 

322 

320 

165 

0-52 

0-99 

1-95 

Metropolitan Railway (London) motor coach . 

49 

52-8 

40-07 

0-77 

1-08 

1-2 

Metropolitan Railway (London) trailer coach . 

56 

52-8 

20-4 

0-39 

0-94 

2-75 

District Railway (London) seven-car train . 

328 

347 

160 

0-49 

1-06 

2-05 

District Railway (London) motor coach with 
luggage compartment..... 

40 

49-5 

27-5 

0-56 

1-03 

1-75 

District Railway (London) motor coach with¬ 
out luggage compartment .... 

48 

49-5 

27-0 

0-55 

1-24 

1-48 

District Railway (London) trailer coach 

48 

49-5 

19-5 

0-39 

1-03 

2-46 

Waterloo and City Railway four-car train 

220 

164 

72 

0-44 

1-34 

3-06 

Waterloo and City Railway motor car . 

50 

47 



1-06 


Waterloo and City Railway trailer . 

54 

35 

... 

... 

1-55 

... 



































































TRACTIVE RESISTANCE AT CONSTANT SPEED 


It is thus seen that one-half ton per foot of overall length is, for the present 
purpose, sufficiently representative of all except the most abnormal cases of rail 
traction. Since the curves of Fig. 2, on p. 6, show that the decrease in tractive effort per 
ton with increasing length of train is relatively slow, owing to the large constant term 
in the denominator of the right-hand side of Aspinall’s formula (see p. 5) and to 
the constant first term in the formula, we may rightly take this figure of one-half ton 
per foot length in transforming the curves from length to weight. The curves given in 
Figs. 10 and 11 have thus been deduced for trains of a total weight of 50, 100, 200, 
400, and 800 tons, and from this point we shall rarely refer back to the former 
curves, but shall base our study on the curves in Figs. 10 and 11. In Fig. 10 the 
speed is given in miles per hour, but in Fig. 11 the speed in feet per second is used, for, 



Fig. 10. Curves of Tractive Resistance in Pounds per Ton for various 

Speeds in Miles per Hour. 


as we shall shortly learn, the use of this expression facilitates some subsequent 
calculations. In Fig. 12 are given corresponding curves in which the kilowatts at the 
axles per ton weight of train are taken as ordinates, and the speed in miles per hour 
as abscissas. In Fig. 13 the total kilowatts at the axles are plotted against the speed. 

Owing to the very lucid and condensed form in which Carter (“ Technical 
Considerations in Electric Railway Engineering ”) handles this subject, and to the 
fact that he bases his determinations on the, in some respects, more logical basis of 
surface resistance, so far as relates to tractive effort at constant speed, and on weight, 
so far as it relates to constant acceleration, the authors have thought it well to 
include verbatim from the above paper the extract in which this subject is dealt with. 
The extract in question is as follows:— 

“ The forces resisting the motion of the train consist of the easily calculated 
positive or negative component due to grade, proportional to the actual weight of the 

15 





























































ELECTRIC RAILWAY ENGINEERING 


train, and the rather uncertain ‘ train resistance,’ composed of journal and flange 
friction, air resistance, etc. There is a lack of reliable data on the resistance offered 



Fig. 11. Curves of Tractive Resistance in Pounds ter Ton for various 

Speeds in Feet per Second. 



Fig. 12. Curves of Power in Kilowatts at the Axles per Ton Weight of Train. 

16 
























































































































































TRACTIVE RESISTANCE AT CONSTANT SPEED 


to the motion of electric trains, which it is hoped will soon be supplied. The classical 
results of Aspinall were obtained from measurements made from behind a locomotive 
and tender, and accordingly do not include the head resistance, which is a very 
important element in the case of electric trains of two or three coaches. The Berlin- 
Zossen high-speed train resistance tests were made with a single coach of a ty r pe 
totally different from those usually employed in this country. Pending the publication 
of more suitable data, the author has combined the results of the above-mentioned 
sets of tests to obtain the working curves of Fig. 14, which be has found to agree 
very fairly with the results of such isolated tests on electric trains as he has been 
able to make. The variable portion is expressed in terms of the dimensions of the 
train rather than of the weight, since it must represent principally air resistance, and 
therefore at any speed can depend only on the external configuration of the train. 



The constant portion of the resistance, which is taken from the above-mentioned 
tests at such low speeds that the static resistance just ceases to be apparent, is 
probably expressed with sufficient accuracy as proportional to the weight, and appears 
to be 21 lbs. to 3J lbs. per ton. The total train resistance is therefore the amount 
deduced from the curves of Fig. 14 increased by 24 lbs. to 3^ lbs. per ton. 

“A light train of given external dimensions will, except at low speeds, meet with 
almost as great a resistance as a heavier-built one of the same dimensions. A train 
of many coaches experiences much less resistance per coach or per ton than one of 
two or three coaches, particularly at high speeds. Allowance is made for these facts 
in the curves of Fig. 14. A long distance high-speed train should, for efficiency, be com¬ 
posed of many coaches, whilst the weight is a secondary consideration. A frequently 
stopping low-speed train, on the other hand, should be built light, but whether it is 
composed of few or many coaches is of small importance as far as efficiency is concerned.” 

We have thus obtained values for the rate of expenditure of energy required at 
E.R.E. \J . C 
























































ELECTRIC RAILWAY ENGINEERING 


the axles in moving the train along a well-ballasted, straight, level line at constant 
speed. This is, of course, a very different case from that generally met in practice. 
The chief difference is associated with the energy required for acceleration. This 
accelerating energy, like the energy required for overcoming the tractive resistance, 
is customarily supplied to the axles by motors, and is subsequently wasted in 
braking. In some roads, however—such, for instance, as the Central London Railway 
—accelerating gradients contribute as much as one-fourth of the energy supplied to 
the train, 1 and similar retarding gradients assist the brakes at stopping. 

In the present condition of engineering nomenclature, it is impossible to avoid 



Fig. 14. Carter’s Train Resistance Curves, giving the Variable Component 

of Train Resistance. 


the employment of mixed units. To facilitate the conversion of speeds and distances 
from one system of units to another, we have given the equivalent values in Tables III., 
IV., V., and AT. 

Table III. 

Equivalent Values of Distance, English and Metric. 



Kilometre. 

Metres. 

Centimetres. 

Miles. 

Feet. 

Inches. 

1 kilometre . 

1- 

1000- 

100000- 

0-621 

3280- 

39400 

1 metre .... 

o-ooi 

1- 

100- 

0-000621 

3-28 

39-4 

1 centimetre . 

o-ooooi 

o-oi 

1- 

0-00000621 

0-0328 

0-394 

1 mile .... 

1-609 

1609- 

160900- 

1- 

5280- 

63400- 

1 foot .... 

0-000305 

0-305 

30-5 

0-0001894 

1- 

12- 

1 inch .... 

0-0000254 

0-0254 

2-54 

0-00001579 

0-0833 

1- 


1 The actual energy supplied by the gradient is, of course, solely dependent on the height through 
which the train descends. On the Central London Railway, the energy supplied by the gradients is 
about fourteen watt-hours per ton mile, or about a quarter of the whole energy supplied to the train. 

l8 





























































































































TRACTIVE RESISTANCE AT CONSTANT SPEED 

Table IV. 

Equivalent Values of Speed, English and Metric. 



Kilometres 
per Hour. 

Metres per 
Second. 

Miles per 
Hour. 

Feet per 
Second. 

1 Kilometre per hour 

1 

0-2778 

•621 

0-911 

1 Metre per second 

3-60 

1 

2-237 

3-280 

1 Mile per hour 

1-609 

0-447 

1 

1-467 

1 Foot per second . 

1-097 

0-3048 

0-682 

1 


Table V. 

Comparative Table of Speeds. 


Kilometres 
per Hour. 

Metres per 
Second. 

Miles per 
Hour. 

Feet per 
Minute. 

Feet per 
Second. 

Kilometres 
per Hour. 

Metres per 
Second. 

Miles per 
Hour. 

Feet per 
Minute. 

Feet per 
Second. 

2 

0-5554 

1-242 

109-3 

1-822 

82 

22-77 

50-92 

4481 

74-70 

4 

1-110 

2-485 

219-7 

3-645 

84 

23-32 

52-18 

4592 

76-54 

6 

1-666 

3-726 

328-1 

5-467 

86 

23-88 

53-40 

4702 

78-34 

8 

2-221 

4-960 

437-4 

7-290 

88 

24-42 

54-68 

4808 

80-16 

10 

2-778 

6-213 

546-8 

9-113 

90 

24-99 

55"61 

4921 

82-01 

12 

3-332 

7-455 

656-1 

10-93 

92 

25-54 

57-12 

5028 

83-80 

14 

3-887 

8-694 

765-1 

12-75 

94 

26-10 

58-37 

5137 

85-63 

16 

4-443 

9-940 

874-8 

14-58 

96 

26-64 

59-64 

5248 

87-44 

18 

4-998 

11-18 

984-2 

16-40 

98 

27-21 

60’68 

5355 

89-20 

20 

5-554 

12-42 

1093 

18-22 

100 

27-78 

62-13 

5468 

9113 

22 

6-108 

13-66 

1202 

20-04 

102 

28-32 

63-34 

5574 

92-92 

24 

6-664 

14-91 

1312 

21-86 

104 

28-80 

64-60 

5684 

94-72 

26 

7-220 

16-15 

1421 

23-68 

106 

29-43 

65"82 

5793 

96-56 

28 

7-774 

17-38 

1530 

25-50 

108 

29-98 

67-08 

5904 

98-40 

30 

8-331 

18-63 

1640 

27-34 

110 

30-54 

68-34 

6014 

100-2 

32 

8-884 

19-88 

1749 

29-16 

112 

31-08 

69-52 

6120 

102-0 

34 

9-441 

21-11 

1858 

30-97 

114 

31-65 

70-79 

6230 

103-8 

36 

9-996 

22-36 

1968 

32-80 

116 

32-20 

72-04 

6342 

105-4 

38 

10"55 

23-59 

2076 

34-62 

118 

32-77 

73-27 

6448 

107-5 

40 

11-10 

24-85 

2197 

36-45 

120 

33-32 

74-55 

6561 

109-3 

42 

11-66 

26-09 

2296 

38-27 

122 

33-87 

75-76 

6667 

1111 

44 

12-21 

27-32 

2404 

40-08 

124 

34-42 

77-00 

6776 

112-9 

46 

12-77 

28*56 

2514 

41-90 

126 

34-99 

78-24 

6886 

114-7 

48 

13-32 

29-82 

2624 

43-72 

128 

35*54 

79-52 

7024 

116-6 

50 

13-88 

31-06 

2734 

45-56 

130 

36-10 

80-77 

7108 

118-4 

52 

14-44 

32-30 

2842 

47-36 

132 

36-64 

82-00 

7216 

120-2 

54 

14-99 

33-54 

2952 

49-20 

134 

37-21 

83-21 

7323 

122-0 

56 

15-54 

34-76 

3060 

51-00 

136 

37-76 

84-44 

7432 

123-8 

58 

16-10 

36-02 

3169 

52-73 

138 

38-32 

85-75 

7541 

125-7 

60 

16-66 

37-27 

3281 

54-67 

140 

38-87 

86-98 

7654 

127-6 

62 

17-21 

38-50 

3388 

56-48 

142 

39-43 

88-18 

7760 

129-3 

64 

17-77 

39-76 

3499 

58-32 

144 

3998 

89-44 

7872 

131-2 

66 

18-32 

41-00 

3608 

60-12 

146 

40-54 

90-66 

7979 

133-0 

68 

18-88 

42-22 

3716 

61-94 

148 1 

41-10 

91-90 

8088 

134-8 

70 

19-43 

43-49 

3827 

63-79 

150 

41-64 

93-18 

8202 

136-7 

72 

19-99 

44-72 

3936 

65'60 

152 

42-21 

94-39 

8364 

138-4 

74 

20-55 

45-95 

4044 

67-41 

154 

42-76 

95-63 

8416 

140-3 

76 

21-10 

47-18 

4152 

69-24 

156 

43-32 

96-29 

8530 

142-1 

78 

21-66 

48-46 

4265 

71-08 

158 

43-87 

98-12 

8634 

143-9 

80 

22*21 

| 

49-60 

4874 

72-90 

160 

44-43 

99-40 

8748 

145-8 


19 


C 2 

























































ELECTRIC RAILWAY ENGINEERING 


Table VI. 

Comparative Table of Speeds. 


Miles per 
Hour. 

Feet per 
Minute. 

Feet per 
Second. 

Kilometres 
per Hour. 

Metres per 
Second. 

| Miles per 
Hour. 

Feet per 
Minute. 

Feet per 
Second. 

Kilometres 
per Hour. 

Metres per 
Second. 

2 

176 

2-934 

3-218 

0-894 

52 

4576 

76-28 

83-66 

23-24 

4 

352 

5-868 

6-436 

1-788 

54 

4752 

79-21 

86-88 

24-13 

6 

528 

8-802 

9-654 

2-682 

56 

4928 

82-14 

90-09 

25-03 

8 

704 

11-73 

12-87 

3-576 

58 

5104 

85-08 

93-32 

25-92 

10 

880 

11-67 

16-09 

4-47 

60 

5280 

88-02 . 

96-54 

26-82 

12 

1056 

17-60 

19-31 

5-364 

62 

5456 

90-96 

99-75 

27-73 

14 

1232 

20-53 

22-53 

6-258 

64 

5632 

93-84 

102-9 

28-60 

16 

1408 

23-47 

25-74 

7-152 

66 

5808 

96-82 

106-1 

29-50 

18 

1584 

26-40 

28-96 

8-046 

68 

5984 

99-74 

109-4 

30-38 

20 

1760 

29-34 

32-18 

8940 

70 

6160 

102-7 

112-6 

31-29 

22 

1936 

32-27 

35-40 

9-834 

72 

6336 

105-6 

115-8 

32-18 

24 

2112 

35-20 

38-60 

10-72 

74 

6512 

108-5 

119-0 

33-07 

26 

2288 

38-14 

41-83 

11-62 

76 

6688 

111-4 

122-3 

33-96 

28 

2464 

41-06 

45-06 

12-51 

78 

6864 

114-4 

125-5 

34-86 

30 

2640 

44-01 

48-27 

13-41 

80 

7040 

117-2 

128-7 

35-76 

32 

2816 

46-92 ■ 

51-48 

14-40 

82 

7216 

120-2 

131-9 

36-65 

34 

2992 

49-87 

54-70 

15-19 

84 

7392 

123-2 

1351 

37"54 

36 

3168 

52-81 

57-92 

16-09 

86 

7568 

126-1 

138-3 

38-44 

38 

3344 

55-74 

61-14 

16-98 

88 

7744 

129 0 

141-6 

39 32 

40 

3520 

58-68 

64-36 

17-88 

90 

7920 

132-0 

144-8 

4023 

42 

3696 

61-61 

67-57 

18-77 

92 

8096 

134-9 

148-0 

41-12 

44 

3872 

64-54 

70-79 

1966 

94 

8272 

137-8 

151-2 

42-01 

46 

4048 

67-48 

74-01 

20-56 

96 

8448 

140-8 

154-5 

42-90 

48 

4224 

70-41 

77-24 

21-45 

98 

8624 

143-8 

157-6 

43-80 

50 i 

4400 

73-35 

80-45 

22-35 

100 

8800 

146-7 

160-9 

44-70 


20 

































Chapter II 

ACCELERATION 


Force = Mass X Acceleration 

_ Weigh t ^ Acceleration. 

0 

C ONSIDER first an acceleration of 1 mile per hour per second, or R47 ft. per 
second per second. The tractive force required to impart to 1 metric 
ton an acceleration of 1 mile per hour per second 

= X 1*47 = 100 lbs. 

32“2 

Useful Rule .—We have thus the useful rule that on a level track a tractive 
force of 100 lbs. per metric ton, in addition to the force required to overcome the 
tractive resistance, imparts to a train an acceleration of 1 mile per hour per second. 
Strictly speaking, one should make ay additional allowance for the rotational energy of 
the wheels and armatures. 1 This is a matter of from 3 per cent, to 7 per cent, of the 
whole kinetic energy of the train, depending on the load per axle and on the 


1 “A Consideration of the Inertia of the Rotating Parts of a Train,” Storer, “Transactions 
of the American Institute of Electrical Engineers,” Yol. XIX. (1902), p. 165. 

Carter (“ Technical Considerations in Electric Railway Engineering,” paper read before the 
Institution of Electrical Engineers, January 25th, 1906) gives rather higher values for the per¬ 
centage increase in the kinetic energy of the train due to the rotating parts. He sets the matter 
forth as follows :—“ The weight of the train to be employed in calculating the acceleration due 
to any force is a certain spurious ‘ effective w r eight,’ composed of the true weight, and an increment 
due to the rotation of the wheels and armatures. This increment is not difficult to obtain, and 
will be merely stated here. If W be the weight of a wheel, r its radius at the tread, and k its 


radius of gyration, the increment of weight due to the rotation of the wheel is W J . In an 

average steel railway wheel ^ ~= 0*6 approximately. 

“ If W l be the weight of an armature, r 1 its radius, k 1 its radius of gyration, and y the ratio 


of gear reduction, the increment of weight due to the rotation of the armature is W l 


W 1 


k 1 r 1 \ 2 


r r 


For a continuous-current armature 


?) 2 


05 approximately. 


k l \2 

y r) = 

Thus if 


yi 

W = 800 lbs., IE 1 = 1,600 lbs., y = 3, — = 4, the addition for rotary inertia will be approximately 

480 lbs. per wheel and 1,800 lbs. per armature. 

“ In the case of suburban trains operated by continuous-current motors, the amount to be 
added on account of rotary inertia, will usually be some 8 or 10 per cent, of the weight of the 
train, whilst with single-phase alternating-current motors, the increment may amount to double 



ELECTRIC RAILWAY ENGINEERING 

construction of the rotating parts. To avoid complicating the question, this additional 
allowance will not be made, but will subsequently be covered by a margin which will 
also provide for the energy consumed in air-pumps, control apparatus, and, in some 
cases, train and station lighting, and power for auxiliary machinery. 

Table VII. gives values for the tractive force in pounds per ton, required during the 
accelerating interval, in addition to the tractive force necessary for overcoming 
friction. In England, rates of acceleration, so far as traction questions are 
concerned, are almost always expressed either in miles per hour per second, or 
in feet per second per second. 


Table VII. 

Tractive Force and Acceleratinfi Iiate. 


Acceleration expressed 
in metres per second 
per second 

0T12 

0 224 

0-336 

0-447 

0*560 

0-671 

0-784 

0-895 

1-00 

1-12 

1 -225 

1 -335 

Acceleration expressed 
in kilometres per hour 
per second 

0-402 

GO 

O 

Or 

1-21 

1-61 

2-01 

2-42 

2-82 

3-22 

3-62 

4 02 

4-42 

4-83 

Acceleration expressed 
in miles per hour per 
second 

0-25 

0-50 

0-75 

100 

1-25 

1-50 

1-75 

2 00 

2 25 

2-5 

2-75 

3 0 

Acceleration expressed 
in feet per minute 
per second 

22-0 

44-0 

660 

88-0 

110 

132 

154 

176 

198 

220 

242 

264 

Acceleration expressed 
in feet per second per 
second 

0 -366 

0-733 

1-10 

1-47 

1-83 

2-20 

2 -56 

2-93 

3-30 

3-67 

4-04 

4-42 

Tractive force in pounds 
per ton 

25 0 

50 0 

75 0 

100 

125 

150 

175 

200 

225 

250 

275 

300 

Tractive force in kilo¬ 
grammes per ton 

11-3 

22-7 

34-0 

45*5 

56 - 7 

68-0 

79-5 

90-7 

102-0 

114-0 

125-0 

136-0 


Letting 

S = speed, 
a = acceleration, 

D = distance, 

T = time, 

then in any given system of units we have the following fundamental relations:— 

S = a T ; 

D = 1 q T 2 ; 

.'. S = V2 a 1). 

In Fig. 15 (a b, c, d, e and f) six groups of curves of speed and time, distance 
and time, and speed and distance, are given for the accelerating interval. 

From the speed-time curves in Figs. 15a and 15b and the distance-time 
curves in Figs. 15c and 15d we may obtain, for any given time in seconds from 
the start, the speed and the distance covered, employing any practicable 
acceleration. The speed-distance curves of Figs. 15e and 15f are derived directly 


as much, on account of the greater number and weight of armatures and their generally higher 
peripheral speed.” 

See also an article in Engineering for March 9th, 1906, p. 295, entitled “ Energy Expended on 
Car Wheel Acceleration.” In this article the calculations are worked out for a special case. 



























Speed- Disc3nce Curves. I Distance-Time Curves. I Speed Time Curves. 











































































































































































































































































































































































































































































































































































































































ACCELERATION 


from the speed-time curves of Figs. 15a and 15b, and the distance-time curves 
of Figs. 15c and 15d. 

Let us now consider the case of a train to be operated over a straight, level 
tiack, with a stop eveiy mile, at an average speed of 30 miles per hour 
between stops, for each 1-mile section. The train must evidently cover such 
a 1-mile section in two minutes. The rates of acceleration and braking will 
be assumed to be equal. 

According to the conditions of practice in any particular case, the rate of 
retardation during braking, would be taken greater than, equal to, or less than 
the rate of acceleration. Moreover, in short runs, constant speed between the pro¬ 
cesses of accelerating and braking is not generally maintained in electrical operations ; 
the power is often cut off directly the maximum speed is reached, or shortlv 
thereafter, and the friction 
of the train is thus used to 
procure a part of the retarda¬ 
tion, a less amount of energy 
being in consequence dissipated 
at the brake shoes. This 
naturally leads to correspon¬ 
dingly improved economy. 

In analysing any particular 
case where such methods are 
employed, the values deter¬ 
mined upon as regards acce¬ 
lerating, braking, and coasting 
are used in the estimation of 
the running conditions. But 
since these details of operation 
vary enormously in different 
eases according to the conditions 
of service, one would , by endea¬ 
vouring to take them into con¬ 
sideration in studying the 
general case, simply lessen the 
*value of the broad conclusions 
ut which one wishes to arrive. 

Therefore, in the first instance, 
v T e shall assume equal rates 
of acceleration and retardation. For the interval not required for these tw y o 
operations, v T e shall assume that the train is run at constant speed. A special 
study will subsequently be made of the extent of the error in the results, con¬ 
sequent upon employing these assumptions. When the study of the general case 
has been completed, v 7 e shall illustrate the analysis of special cases, and shall 
ascertain and employ the precise rates of acceleration and retardation and the 
amount of “coasting” suitable for obtaining the best conditions in each case. 

For the present purpose it will suffice to briefly illustrate the point involved 
by reference to Figs. 16 and 17, which are taken from Armstrong’s paper, 
entitled “ Some Phases of the Eapid Transit Problem,” read before the American 
Institute of Electrical Engineers (1898, Yol. XV., p. 363). In deriving these curves, 

23 



O 10 20 30 40 SO 60 70 


Time in Seconds. 

Fig. 16. Speed-Distance Time Curves (Armstrong’s). 

Distance = 2,000 feet. 

Time = 75 seconds. 

Rate of Acceleration = 0'93 miles per hour per second. 
Friction = 10 lbs. per metric ton. 

Braking Effort = 100 lbs. per metric ton. 











































ELECTRIC RAILWAY ENGINEERING 


Armstrong has made the assumptions set forth below the titles of Figs. 16 and 17. 
For the purposes of a general survey of the subject, and in view of the conditions 
as regards rolling stock and permanent way, and the low speeds considered, 
Armstrong is not altogether unjustified in taking for the friction at all speeds, 
the mean value of 16 lbs. per metric ton, although, as we have already seen from 
Fig. 2, on p. 6, the friction in pounds per ton varies through a wide range with variation 
in the speed. 1 These two curves (Figs. 16 and 17) are based on an accelerating 
rate of 0'93 miles per hour per second, and upon a braking effort of 160 lbs. per 
metric ton, corresponding to a retardation of 1*6 miles per hour per second. In 
the curve of Fig. 16 the power is cut off immediately at the end of the 
accelerating interval (i.e., at the end of 30 seconds, when a speed of 28 miles per 

hour has been attained, a 
distance of 600 ft. having been 
covered), and the train coasts 
for the next 31 seconds (i.e., 
for the next 1,200 ft.). The 
brakes are then applied, bring¬ 
ing the train to rest after 
75 seconds from the start, the 
distance of 2,000 ft. having 
been covered at the average 
speed of 18*2 miles per hour. 

In Fig. 17 Armstrong 
has illustrated an alternative 
method (shown in the cycle 
o b b 75) of covering the same 
distance at the same schedule 
speed of 18*2 miles per hour, 
sufficient power being kept on, 
until the brakes are applied, 
to maintain the constant speed 
of 25*5 miles per hour attained 
at the end of 27 seconds of 
acceleration. 

By operating on the curve 
o b b 75, instead of on the 
curve o a a 75, 9 per cent, 
lower maximum speed, and, as we shall see later, a lower maximum power, 
is required for a given average schedule speed ; but, as we shall also see 
later, this is at the cost of some 9 per cent, more total energy consumed 
during the run. The relative merits of these two methods, as also that of 

1 “ It may be said that while there is no material error in assuming constant train resistance 
for all cases where the speed does not exceed 25 miles per hour, yet above these speeds there 
is a possibility of error which becomes- a certainty when the speeds reach 40, 50, or 60 miles, 
the amount of error increasing with the speed. This matter is now so well understood that a 
mere mention is sufficient. Very little reasoning will show that the increase of train resistance 
as a function of the speed cannot be left out of consideration in any computations relating to 
high-speed service.”—Gotshall, “Transactions of the American Institute of Electrical Engineers,” 
Vol. XIX. (1902), p. 184. 



Fig. 17. Speed-Distance-Tiiie Curves. 

Distance = 2,000 feet. 

Time = 75 seconds. 

Friction = 16 lbs. per metric ton. 

Braking Effort = 160 lbs. per metric ton. 





































ACCELERATION 


“ acceleration on the motor curve,” cannot well be considered at any length until 
the subject of tractive force and energy is taken up. It may here be 

briefly stated that cycles approaching that illustrated in Fig. 16 and in curve, 
o a a 75 of Fig. 17 are more suitable for frequent stop service at a high average 
speed; but that the longer the run 
between stops, or the lower the average 
speed the more does the cycle employed 
in actual service resemble that illus¬ 
trated by the diagram o b h 75 of 
Fig. 17. The error introduced by 



B— Distance- Time Curves for same accelerations . 


adopting the latter type of diagram 
throughout this preliminary study, is 
the greater the shorter the run between 
stops and the higher the average speed ; 
but the error is on the safe side, and 
immense advantage is gained in obtaining 
a preliminary broad view of the limiting 
factors, to free this necessarily complex 
investigation from as many subsidiary 
considerations as practicable. 

Pieturning to the general case of a 
train to be operated over a straight level 
track with a stop every mile and at an 
average speed of 30 miles per hour for 
each 1-mile section (assuming equal 
rates of acceleration and braking), it is 
evident that the very lowest rate of 
acceleration must enable the train, during 
an accelerating- interval of 60 seconds, 
to cover a distance of 0‘50 miles. Fig. 18a 
shows us that the corresponding rate of 
acceleration is 1 mile per hour per second 
1 1 *47 ft. per second per second). We 
may, if we choose, find from Fig. 15a 
that the speed at the end of 60 seconds 
is 60 miles per hour (reading off the 
speed from the intersection of the 
ordinate at 60 seconds, with the line of 
reference for an acceleration of 1 mile 
per hour per second), although this is 
obvious without consulting a diagram. 

The speed-time curve would thus 
be the full line curve of Fig. 18a, which 
is marked “1 mile” to indicate that 

an accelerating rate of 1 mile per hour per second is employed. The accelerating 
half is transferred directly from Fig. 15a, and the braking half is merely the reverse 
of this curve. The corresponding distance-time curve is given in Fig. 18b ; the 
accelerating half is transferred directly from Fig. 15c. Fig. 18c is transferred 
directly from Fig. 15e for an acceleration of 1 mile per hour per second, and gives 

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C -Speed-Distance Curves for same accelerations. 


Fig. 18 (A, B, and C). Speed-Distance-Time 
Curves. 

For a one-mile run at an average speed of 30 miles per hour ; 
time from start to stop = 2 minutes. 














































































































































ELECTRIC RAILWAY ENGINEERING 


the speeds as ordinates in terms of distances as abscissae. These are the three 
characteristic curves for the case of a train travelling over a 1-mile section at an 
average speed of 30 miles per hour for the minimum rate of acceleration and 
braking permissible for this schedule. 

Let us next take an acceleration of 1*4 miles per hour per second (2‘07 ft. per 
second per second), and let it be assumed that the braking is at an equal rate. 

Let x = duration of accelerating interval in seconds. 

Then 120 — 2 x = duration of constant speed interval. 

The distance in feet covered during acceleration — 0‘5 X 2'07 x x 2 . 

Speed in feet per second attained at end of accelerating interval = 2‘07 x x. 

Distance in feet covered at constant speed = 2‘07 X x X (120 — 2 x). 

Distance in feet covered during braking = 0 5 X 2 07 X x~. 

Total distance — 5,280 ft. 

From these values we readily derive the following equation :— 

2-07 x a - — 248 x -f 5,280 = 0; 


xr 


— 120 x + 2,540 = 0; 


.-.a; 2 - 120 x + 3,600 = 1,060; 
x — 60 = - 32-5 ; 
x = 27'5 seconds. 

From Fig. 15c we see that after 27*5 seconds of acceleration at a rate of 1*4 miles 
per hour per second a distance of 0T5 miles will have been covered; and from 
Fig. 15a it is seen that a speed of 38 - 8 miles per hour will have been attained. 
During the succeeding 65 seconds the speed will be constant at this value, and a 
distance of 0 - 70 miles will be covered at constant speed. During the remaining 27'5 
seconds the brakes will be so applied as to produce a retardation of 1 4 miles per 
hour per second, and the train will arrive at the end of the mile section in just 
120 seconds. 

If we denote by 

x the duration of the accelerating interval in seconds, 

T the duration of the run from start to stop in seconds, 

A the distance from start to stop in feet, 
a the rate of acceleration in feet per second per second, 




Instead of by calculation, one may often prefer to determine the accelerating 
interval by one or two trials from the curves of Figs. 15a to 15f. The three 
characteristic curves for this accelerating rate of D4 miles per hour per second are 
shown in the 1*4 mile curves of Figs. 18a, 18b, and 18c; and it will be readily 
perceived that they are merely made up b} r combining curves available in Figs. 15a 
to 15f. 

Similar sets of characteristic curves for other accelerations, but for the same 
mean speed of 30 miles per hour and the same distance of 1 mile, are also given in 
Figs. 18a, 18b, and 18c. 

For this case of a level 1-mile section, corresponding charts of curves have been 
worked out for average speeds of 20, 25, 30, 35, 40, and 45 miles per hour. These are 
not all reproduced here; but in Fig. 20 the whole group of speed-time and distance-time 
curves for this level 1-mile section are reproduced to a small scale. Corresponding 
groups of curves for distances between stops of 05 miles, 2 miles, 4 miles, and 
8 miles, are given in Figs. 19, 21, 22, and 23. These charts are very useful for 

26 





































































































































































































































































































































































































































































































































































Fig. 20. Speed-Time and Distance-Time Curves for various Accelerations and Average Speeds. One-Mile Run. 






















































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































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Fig. 23. 


Speed-Time akd Distance-Time Corves for various Accelerations and Average Speeds. Eight-Mile Ron. 





























































































































































































































































































































































































































































































































































































































































































































































































































































































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ACCELERATION 



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ELECTRIC RAILWAY ENGINEERING 


reference in practice. They show the conditions and limitations in a way unattain¬ 
able with mere formulae. After having determined the suitable running conditions 
for a given case by reference to charts, it often becomes expedient to resort to 
formulae, but this is largely a matter of individual preference. In the initial stages 
of an investigation, however, the use of charts of this kind is far more instructive 
than the use of formulae, and it is a matter for regret that in the limits of a printed 
page such charts must be on so small a scale as to considerably impair then- 
usefulness. 

The five curves of the second group of the upper row in Fig. 24 have been 
plotted, for a 1-mile section, to show the maximum speeds required for different 
accelerating rates for average speeds of 25, 30, 35, 40, and 45 miles per hour. By 
“average” speed we shall in this treatise designate the mean speed while the train is 
in motion, i.e., the mean speed for a run from start to stop. By “schedule” speed 
we shall designate the mean speed including stops. Thus the five groups of curves 
in the upper row of Fig. 24 represent the average speeds from start to stop, for 
various accelerating rates as abscissse, for runs of half a mile, 1 mile, 2 miles, 4 miles, 
and 8 miles between stops. These “average” speeds approach more closely to the 
corresponding “ schedule ” speeds the shorter the duration of the stops. Thus for stops 
of 0 seconds duration, i.e., for the limiting case where the train is started off into the 
next section the instant it is brought to rest after running over a given section, the 
“ schedule ” speed becomes equal to the average speed. The second horizontal row 
of groups of curves in Fig. 24 are calculated on the basis of 10-second stops at 
stations, and the schedule speed for any given rate of acceleration and for any given 
length of run between stops is lower than the average speed, and by a rapidly 
increasing percentage with increasing schedule speed. The lowest horizontal row of 
groups of curves is calculated for 20-second stops. 

These curves bring out very forcibly the limits of attainable “average” and 
“ schedule ” speeds. Thus for a 1-mile run between stops an average speed of 
45 miles per hour is practically unattainable. The minimum rate of acceleration 
possible with such a schedule is 2*25 miles per hour per second; and the 
maximum speed then necessary is 90 miles per hour. Nevertheless, its inclusion 
in the investigation serves to define the problem. 

An “ average ” speed of 45 miles per hour with one stop per mile, and a 
duration of 20 seconds per stop, involves a total interval of 


45 X 20 
60 


= 15 minutes 


out of every hour during which the train is at rest. 
The corresponding “ schedule ” speed is therefore 


60 - 15 
60 


X 45 — 33'8 miles per hour. 


In practice a “ schedule ” speed of 30 miles per hour with one stop per mile 
represents the upper commercial limit, and even this “schedule” speed is of 
doubtful expediency for a route with such frequent stops. 

By a comparison of the corresponding curves for 1 mile and half-mile 
sections it is apparent that a schedule speed of 22 miles per hour is, for a route 
with half-mile runs, about equivalent, on the score of ultimate possibility, to a 
schedule speed of 30 miles per hour for a route with 1-mile runs. 

The curves of Fig. 25 are drawn to show the minimum accelerating rates 
possible in order to accomplish given average and schedule speeds over routes 

28 





Curve A. Maximum Speed = 1-5 X Average Speed. 
Curve B. Maximum Speed = 2 x Average Speed. 



















































































































































































































































































































































































































































































































































































ACCELERATION 


composed respectively of sections with lengths of half a mile, 1 mile, 2 miles, 
4 miles, and 8 miles from start to stop. From Fig. 25 we see, for example, that 
with one stop per mile and a limiting acceleration of 1 mile per hour per second 
the highest theoretically obtainable schedule speed with stops of 0 seconds duration 
is 30 miles per hour, and the corresponding schedule speed with 20-second 
stops, is, for the same rate of acceleration, only 25 miles per hour. This rate 
of acceleration (1 mile per hour per second) would exceed the possibilities of the 
best steam service, such high rates of acceleration not being practicable with 
steam-hauled trains of any length. The values given in Table VIII. are deduced 
from Fig. 25. 


Table VIII. 

Corresponding Schedule Speeds in Miles per Hour for Runs of Following 

Distances between Stops. 


O - b 

<X> £ . 

i Mile. 

1 Mile. 

2 Miles. 

4 Miles. 

8 Miles. 

c: . § 



















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39 

0-4 

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12 

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18 

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26 

25 

38 

37 

35 

55 

53 

51 

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39-5 

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57 

55 




1-2 

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21 

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33 

30 

28 

46 

43-5 

40-5 

65 

62 

60 




1-4 

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36 

32 

29-5 

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43-5 







1-6 

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1-8 

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48-5 







2-0 

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22-8 

42-5 

38 

34 










2-2 

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23-6 

445 

39-5 

35’5 










2-4 

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24-4 

46-5 

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37 










2-6 

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25-1 













2-8 

35-5 

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25-8 













3-0 

37-0 

31 

26 - 6 














The three curves of Fig. 26 are derived by taking 90 per cent, of the values 
of the curves of Fig. 25 for 20-second stops and for maximum speeds 50 per cent, 
higher than the average speeds. These curves afford approximate locii of the 
schedule speeds attainable with electric traction for various lengths of run between 
stops. A braking rate of 2 miles per hour per second is quite permissible. 
Hence, with continuous current motors, schedules ranging between the two upper 
curves become practicable so far as relates to the exclusive consideration of speed 
and time, though they would require very heavy electrical equipments when 
expressed as a percentage of the total train weight. 

With electric traction, it becomes possible to distribute the driving effort 
amongst the axles of some or all of the carriages, and accelerating rates above 
2 miles per hour per second sometimes become practicable; hence, were it not for 
the question of the instantaneous loads imposed upon the system and the weight 
of the electrical equipment required to be carried on the train (both of which 

29 















































ELECTRIC RAILWAY ENGINEERING 


limitations will be discussed later 1 ), schedule speeds of over 30 miles per hour 
and ‘20-second stops would be practicable with one stop per mile. Indeed, tests 
have shown as high an acceleration as 3 miles per hour per second to have 
been attained by electric traction. A curve is given in Fig. 27 of a run made 
over a 5,360-foot section with an electric train weighing 65 metric tons and 
made up of motor-cars without trailers. The average rate of acceleration during 



Fig. 2(J. Curves of Limiting Attainable Schedule Speeds for Given 
Mean Rates of Acceleration and Braking. 


Curve A. —Mean rate of acceleration and braking 

»j j> >> yj 

r _ 

>> a >? j > 


= 2*0 miles per hour per second. 

~ 1 ^ n it iy 

= 1 0 )> ft * ff 


the first 5 seconds is seen to be nearly 3 miles per hour per second. This rate 
of acceleration was, however, not maintained, and the retardation was at a lesser 
rate; although the maximum speed was 47 miles per hour, the average speed 
was but 35 miles per hour. This was a very high average speed for so short 
a section, and it would rarely be practicable to attain it; for, as we shall 
subsequently show, the amount of power required during acceleration is excessive, 

1 These limitations suffice to prevent the practicability of schedule speeds of over 30 miles 
per hour with one stop per mile, and even so high a schedule speed with one stop per mile is of 
doubtful practicability from the commercial standpoint. 

30 
























































ACCELERATION 


weight 
if 


important to 
is the case, 
the 3 miles 


and the 
is enormous, 
heating. It is 
note that this 
although, could 
per hour per second accele¬ 
rating rate be maintained, 
we see from the curves of 
Fig. 25 that a 50 per cent, 
higher average speed (52 miles 
per hour) would be practicable 
without exceeding any limita¬ 
tions introduced up to this 
point of the investigation. 
Mr. Mordey, in discussing 
tests on the Liverpool Overhead 
Railway, has shown that two 
or three seconds after starting, 
the accelerating rate reached 
28 miles per hour per second. 

Turning back to Fig. 24, 
the general form of the upper 
curves (i.e ., those for average 
speeds of 45, 40, and even 
35 miles per hour) affords 
evidence, quite aside from the 
question of power and weight 


of the electrical equipment requiring to he carried on the train 
the service is to be continuously maintained without undue 



SO 60 
Time 


70 80 90 100 

in Seconds . 


120 130 140 ISO 


Fig. 21 


Speed-Time Curve for a 65 (metric) ton Electric 
Train of Motor Cars (Xo Trailers). 

5,300 foot run power on for 4,080 ft. Watt-hours per ton-mile = 142.— 

“Trans. Am. Inst. Elect. Eng.,” Vol. XIX., p. 844. 


UVjU null Vi. ^/V M VJ. ^ O - 

of equipment, of the commercial impracticability of maintaining an average speed 
of much over 30 miles per hour with one stop per mile. 

For the purposes of this general investigation, the diagrams are drawn for 



Fig. 28. Speed-Time Curve for a Constant 
Acceleration of 2 - 2 Miles per hour per 
second. Average Speed 40 Miles per hour. 



O /O 20 30 40 30 60 /O BO 90 '00 


Time m Seconds 

Fig. 29. Speed-Time Curves for a Mean 
Acceleration of 2 - 2 Miles per hour per 
second. Average Speed 40 Miles per hour. 


a constant rate of acceleration throughout the accelerating interval. In practice, 
however, the rate of acceleration is itself variable, being at first rapidly increased 
to above the average rate and then decreased until constant speed is reached. By 
























































































ELFXTRIC RAILWAY ENGINEERING 

such variation of the rate of acceleration, it is practicable to employ a high average 
rate of acceleration without undue strain upon the rolling stock and permanent way, 
and without much discomfort to passengers. This is the more necessary the higher 
the average rate of acceleration. Thus the curve of Fig. 28, reproduced above, would 
in reality he replaced by a curve more like that in Fig. 29. 

The characteristic of a series motor plays an important part in determining the 
form of the upper part of the acceleration curve. In the generally employed sense, 
the acceleration occurs on the “ motor curve ” from the point where the resistance in 
series with the motor has finally been completely cut out. From this point onward 
the speed increases at a slower rate, which is a function of the motor’s speed curve, 
the current falling off as the speed increases, until the watts input falls to the value 
required to overcome the train resistance at constant speed. It is frequently the case 
that the resistance is completely cut out before more than two-thirds of maximum 
speed is reached, and the remaining one-third is run on the “ motor curve.” The 

point where operation on the “motor curve ” 
commences is a function of the design of 
the motor and of the rate of acceleration 
employed. This must for the present be 
overlooked, as it would hopelessly involve 
the preliminary study of the mechanics of 
electric traction were it necessary to intro¬ 
duce at this stage the varying conditions 
peculiar to the use of several types of motor, 
or even to consider the varying charac¬ 
teristics of motors of the same class. The 
thorough study of this matter of accelera¬ 
tion on the “ motor curve ” must be taken 
up at a later stage. The difference intro¬ 
duced in the speed-time curve for the case 
already illustrated by the diagrams in 
Figs. 16 and 17 is seen in Fig. 30, where 
the case of running on the motor curve is 
shown in the curve 0 c c 75, which may be 
compared with the curve 0 b b 75, drawn 
in dotted line, which is reproduced from Fig. 17. As we shall see later, the 
cycle 0 c c 75 requires the lowest maximum input and the lowest total input for 
maintaining the specified service, and it is a point of great economic importance 
to accelerate on the “motor curve” to the extent permissible with high accelerating 
rates. For an equipment employing a given design of motor, the higher the initial 
accelerating rate the sooner will the series resistance be cut out, and the sooner will 
the point of economical acceleration on the motor characteristic be reached. The 
average rate of acceleration and the average speed between stops will, however, be the 
more greatly reduced the sooner the point of acceleration on the motor characteristic 
is reached. 

A few additional groups of speed-time-distance curves have been constructed with 
a view to showing some striking contrasts occurring as the result of variations in the 
factors of rate of acceleration, average speed, and distance between stops. In Fig. 31 
are shown for an average speed of 40 miles per hour the speed-time (S.-T.) and 
speed-distance (S.-D.) curves for accelerating rates of 1, 2, and 3 miles per hour 

. 32 



Fig. 30. To ILLUSTRATE CASE OF RUNNING 
on “ Motor Curve.” 









































ACCELERATION 




























































































































































































































































ELECTRIC RAILWAY ENGINEERING 


per second. Similar charts for other speeds have been worked out, but are not 
reproduced in this treatise. 

From a comparison of these various curves it is very apparent that the accele¬ 
rating conditions exert an ever diminishing influence the greater the distance between 
stops, and the lower the average speed for a given distance between stops. High 
rates of acceleration are the less necessary or desirable the greater the distance 
between stops. A large number of useful conclusions may be drawn from curves 
based on these and similar charts. 

In the left-hand vertical column of Fig. 32 are plotted S.-T.-D. curves for an 
accelerating rate of 2 miles per hour per second, and an average speed of 60 
miles per hour, for distances between stops of 2, 4, and 8 miles. While for a stop 
every 2 miles an average speed of 60 miles per hour is only just possible by 
calculation at this rate of acceleration, and quite unattainable in practice, it becomes 
quite practicable with one stop per 8 miles. 

In the right-hand vertical column of Fig. 32 are given corresponding curves for 
an accelerating rate of 3 miles per hour per second, which, as we shall see later, 
requires too great a consumption of energy during the accelerating period and too 
heavy an equipment to be commercially practicable. 

Both vertical columns of Fig. 33 relate to runs of 4 miles between stops at 
various speeds. The groups of curves in the left-hand column correspond to an 
accelerating rate of 1 mile per hour per second, which, while moderate for electric 
traction, is too high for steam traction ; the accelerating rate in the groups of curves 
in the right-hand column of Fig. 33 is 2 miles per hour per second, which is 
practicable with electric traction, but is unattainable by steam-hauled trains. Looked 
at with these facts in mind, the two sets of groups of curves show at a glance the 
great increase in schedule speed rendered practicable by electric traction, even with 
such a comparatively long run as 4 miles between stops. 

It is evident from the results of our investigation up to this stage that, altogether 
apart from the energy limitations, there are limitations to the practically attainable 
schedule speeds, which limitations are the more narrow the shorter the run between 
successive stops. 

We shall now set forth a general method for investigating this matter in 
any case which may arise, always assuming that the rate of acceleration equals 
the rate of retardation, that this rate is constant in each case, and that during 
the time intervening between acceleration and retardation, constant speed is 
maintained. 

We shall designate by— 

A the distance from start to stop in feet; 
x the time of acceleration in seconds ; 

T the total time from start to stop in seconds ; 

V max . the maximum speed between stops in feet per second; 

V av the average speed between stops in feet per second; 
b the rate of acceleration in feet per second per second ; 

B the minimum rate of acceleration which will carry the train over the 
distance A in a specified time T, the train being then abruptly brought 
from the maximum speed to rest by the application of an infinite 
braking effort. 

Then A = l BT~; .*. B = —* 


34 


Speed -Distance 



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Fig. 32. Speed-Time-Distance Curves for an Average Speed of CO Miles per Hour 
for Two, Four, and Eight Mile Runs from Start to Stop. 

35 


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Fig. 33. Sreed-Distance-Time Curves for Four-Mile Section. 

30 
















































































































































































































ACCELERATION 

If A and T are given, B can be found by means of the curves in Fig. 15. Let 
x , . 

a = ip, i.e., a is equal to the fraction of the total time which is devoted to 
acceleration. 

From these premises the two following equations may be derived 1 :— 

^nin v 1 ^ I ^ 


1 — a 


(II.) 


B 2 a (1 — a) 

These two equations, I. and II., are correct for all distances A, for all average 
speeds V av , and for all accelerating rates b. Their use may be simplified by plotting 


1 Equations I. and II. are derived as follows :— 
We have- 

A = \ 

av. 


A — V T 

A — v av. - 1 - ’ 


and also 


V Y 

A = x + V (T — 2x) + x, 

9 1 max. \ 1 1 9 


which simplifies into 

A = V max . (T - x). 
From (1) -and (2) we have— 


We also have given— 


av. 

v 


v av . T. = V max (T - x); 

T 1 


T - x i - x 
- T . 


V 


T ’ 


( 1 ) 


( 2 ) 


( 3 ) 

(B 


which is Equation I. 
We also have— 


or 


but 


We also have given— 
From (7) and (8) we obtain 


but 


V aT . 


1 - a 


V = b. x, 

max. 


b _ 

X 


V = 

"’■’X. — 

b = 


max. — X - X 

A 

x (T - x)' 


B 


2 A 
T 2 ’ 


r^2 


B 2x (T - x)' 


T = - (from (4)); 
a 


b 

B 


x 


2 a? [ - - x 


(5) 

( 6 ) 


(B 

(») 


or 


B 2 a (1 - a) 


which is Equation II. 


37 












ELECTRIC RAILWAY ENGINEERING 



Values of a (a = y) 

Fig. 34. 


them in the two curves, (I.) and (II.), of Fig. 34, with values of a as abscissae, and 
with the values 


respectively as ordinates. 1 


Y*** and 

’ av. 


b 

13 


As ° lax ' and are ratios, we may employ the curves of Fig. 34 without reduction from mile 

’ av. ™ 

or kilometres per hour (as the case may be) to feet per second, or from miles per hour per second to 
feet per second per second. 


33 














































































































ACCELERATION 


The use of the curves in Fig. 84 may be best illustrated by means of an example. 
Given a 1-mile section (A = 5,280 ft.), average speed = 80 miles per hour ; 

. *. T = 120 seconds. 
p _ 2 A _ 2 X 5,280 
T 2 “ 120 3 

= 0'78 ft. per second per second. 

Let us ascertain the maximum speed (V max .) and the minimum rate of accelera¬ 
tion (b) which will he necessary when x equals 18 seconds. 


0 = | = 0-15, 

i.e., the accelerating interval x is 15 per cent, of the total time T from start to stop. 
From curves I. and II. of Fig. 34 we find respectively that 

= 1‘20, and that = 3 9; 

’ av. 

V raax . = 1*20 X V av . = 1*20 X 30 = 36 0 miles per hour. 

And b = 3*9 x B =: 3 - 9 X 0 - 73 = 2*85 ft. per second per second, or T95 miles 
per hour per second. 

Suppose, on the other hand, that we want to maintain this same average speed, 
and that we wish to accelerate and retard at the rate of only F5 miles per hour per 
second. How many seconds will be required for acceleration ? 

B remains equal to 0'73 ft. per second. 
b = 1*5 X 1*47 = 2”20 ft. per second per second. 

b _ 2-20 
B “ 0-73 


= 3-02. 


From curve II. of Fig. 34 we find 


a 


= ijr ) = °’ 21 5 


. •. x = 0’21 T = 0 21 X 120 = 25'2 seconds. 

The acceleration will thus occupy 25*2 seconds. 

From curve I. of Fig. 34 we find that 

^ max. —- 1-26 ; 

V av . 

y 126 x 30 = 37-8 miles per hour is the maximum speed required. 


39 




tractive Force in pounds per Ton Tractive Force in pounds per Ton. Tractive Force in pounds per Ton . 



Time in Seconds. 

A.- 50- ton train . 



Time in Seconds 

B.- 200-ton train . 



Time in Seconds. 

C.- 800-ton train . 


Curves shown thus -_ relate to Speed . 

Figs. 35a, 35b, and 35c. Charts showing 
Tractive Force with various Accele¬ 
rating Eates for Trains of Different 
Weights 


Chapter III 

THE TRACTIVE FORCE AND THE POWER 
AND ENERGY AT THE AXLES 

U P to this point the relations between 
speed, distance, and time have alone 
been considered. The corresponding tractive 
force must next be discussed. 

During acceleration at a constant rate on 
a level the tractive force is made up of two 
components, the one constant and a function of 
the rate of acceleration and the other a variable 
component and a function of the speed from 
instant to instant. During operation on the 
level at constant speed the tractive force is also 
constant, and is a function of the speed. The 
tractive force required for acceleration, and 
corresponding to various rates of acceleration, 
has already been given in Table VII. To these 
values must be added the variable tractive 
force from instant to instant required for over¬ 
coming the tractive resistance as the speed 
increases. The percentage difference which 
this introduces is a function of the rate of 
acceleration and of the weight of the train. 
In Figs. 35a, 35b, and 35c are given curves 
showing for 50-ton, ‘200-ton, and 800-ton trains, 
the tractive force required per ton weight of 
train to maintain various rates of acceleration 
during the accelerating period. It is seen that 
throughout this wide range of train weights 
( i-e ., from 50-ton to 800-ton trains) the variation 
with the weight is not great, and in order to 
simplify the calculations we shall, for sub¬ 
sequent work, take as the tractive force per ton 
during acceleration that corresponding to a 
200-ton train as sufficiently correct for all train 
weights. 

Thus the curves of Figs. 36a, 36b, 36c, and 
40 





























































































































































































































































































































Dotted Curves relate to Speed. 

A. 


Dotted Curves relate to Distance 

c. 




Time in Seconds. Time in Seconds . 


B. D. 




0 10 20 30 40 SO 60 70 80 90 100 110 120 130 140 0 10 20 30 40 SO 60 70 80 90 100 110 120130 140 


Time in Seconds. 


Time in Seconds. 


Figs. 36a, 36b, 36c, and 36 d. Chart showing Tractive Force with various Accelerating 

Rates for 200-Ton Train. 


41 



























































































































































































































































































































































































































































ELECTRIC RAILWAY ENGINEERING 


36d, which really refer to the tractive force per ton weight of train for a 200-ton 
train, will be employed for all train weights, and it may be kept in mind that this 



Fig. 37. Curves of Speed, Tractive Force, Power, and Energy at Axle. 200-Ton Train 

OPERATED BETWEEN STOPS AT AN AVERAGE SPEED OF 30 MlLES PER HOUR WITH ONE STOP 

per Mile 


gi' e,s somewhat too liberal values for long trains and somewhat too low values for 
short trains. 

Let us take the case of a train operating with one stop per mile at an 

42 






































































































































































































































































































THE TRACTIVE FORCE AND POWER AT THE AXLES 


average speed of 30 miles per hour between stops. Assuming constant rates of 


acceleration and retardation and a 
acceleration to the commencement of 
accelerating rates of 1*0, 1*4, 1*8, and 
2*2 miles per hour per second will be 
those already given in the curves of 
Fig. 15 and in the curves of column C 
of Fig. 20. These curves are repeated 
in the upper row of Fig. 37. The 
corresponding tractive force-time curves 
are given in the second row, the constant 
speed figures relating to a 200-ton train. 1 
The rate of expenditure of energy at the 
axle, in foot-pounds per second per ton 
weight of train, is given in the third row. 


uniform speed from the completion of 
retardation, the speed-time curves for 


ZQ 

Z-4 

zo 

l 6 
12 

•8 


n— 











.5= o 

c- u 

-o £ 











A) s_ 
fVS CD 











h D 

CD ^ 











CD O 
CD-£Z 
<X) s_ 











4_ <D 

O CL 











<S'e 

F 

"npn 









Cr 

in watt-hours,per.ton mile. 




0 20 


40 


6o 6o 


100 120 


As a kilowatt equals 737 foot-pounds per 38 - Curve of Watt-Hocrs at Axles per 

Ton-Mile for 200-Ton Train operating with 


One Stop per Mile at an Average Speed of 
30 Miles per Hour between Stops, and with 
varying Rates of Acceleration. 


second, the energy expended in kilowatts 
at the axle per ton weight of train moved, 
is readily deduced, and is given in the 
fourth row of curves. The fifth row of 

curves shows the total watt-hours at the axle per ton weight of train which, at any 
given time from the start, have been consumed. Hence the value at the point of 
cutting off the current represents the watt-hours at the axle per ton-mile for the 
entire run from start to stop. 

This, for the different rates of acceleration, is as follows : — 


Table IX. 

Consumption of Energy at Axles in Watt-hours per J'on-Mile, One Stop per Mile. 


Rate of Acceleration in 
Miles per Hour per Second. 

Watt-hours at the Axles per 
Ton-mile for a iOO-ton Train 
operated at a Schedule Speed 
of 30 Miles per Hour betwten 
1-mile Stops. 

1*00 

117 

1*40 

57 

1*80 

50 

2*20 

47 


The results in Table IX. are plotted in the curve of Fig. 38. It is evident 
that, so far as relates to obtaining a low rate of expenditure of energy at the 
axles in watt-hours per ton-mile, a high rate of acceleration is desirable. It will 
be seen later, however, that this may entail an unduly heavy equipment and 
other disadvantages. 

An interesting point to note is that the maximum instantaneous load at the 
axles required for this average speed of 30 miles per hour between stops and one 
stop per mile, first decreases with increasing rates of acceleration, and after passing 

1 A representative 200-ton train will be assumed in much of the following discussion. Rough 
modifications of the results will generally give a basis for sufficiently accurate values for lighter 
and heavier trains. 


43 






























ELECTRIC RAILWAY ENGINEERING 


through a minimum at a rate of acceleration of about 13 miles per hour per 
second, again increases with higher rates of acceleration. This may be seen from 
the third and fourth rows of diagrams in Fig. 37, but is more clearly brought out 
in the curve of Fig. 39. 

The average power at the axles in kilowatts per ton weight of train for a 
200-ton train operating at an average speed of 30 miles per hour between stops, 


3* 


*4 


16 


•8 


o -8 1-6 2*4 3-2 

Fig. 40. Curve of Average Power 
from Start to Stop in Kilowatts 
at Axles per Ton Weight of Train 

OPERATED WITH ONE STOP PER MlLE, 

at an Average Speed of 30 Miles 
per Hour between Stops, for 
Different Rates of Uniform 
Acceleration. 

and with one stop per mile for these four rates of acceleration, is readily derived 
from the values in Table IX., and is given in Table X. 

Table X. 

Average Power at Axles in Kilowatts per Ton, One Stop per Mile. 


Rate of Acceleration in 
Miles per Hour per Second. 

Average Power at Axle. 

l-o 

3 - 50 kilowatts 

1*4 

1*71 

>> 

1-8 

1-50 

>> 

22 

1-41 

>5 


E „ 







oo 5 







’■>< o 







-i—> c 

E--.S 

'CD Q_v_ 
^ O ^ 
-O-h^ Q 








V 





Q. 

&oS 










-Qe 







—Rate 
miles 

of 

per 

acce 

'hoi 

iler< 
r pe 

atio 
r se 

n in 
icor 

d. 



Hate of Acceleration m Miles per Hour 
per Secona. 

Fig. 39. Curve of Maximum Instantaneous 
Power at Axles in Kilowatts per Ton 
Weight of Train. 200-Ton Train operated 
with One Stop per Mile at an Average 
Speed of 30 Miles per Hour between 
Stops for different Rates of uniform 
Acceleration. Rate of Retardation 

TAKEN AS EQUAL TO RATE OF ACCELERATION. 


The results in Table X. are plotted in Fig. 40, and this also is in favour of 
a high accelerating rate. 

For the same schedule speed of 30 miles per hour, but with but one stop 
per 2 miles, the calculations will be carried out tabularly instead of by diagrams. 
The steps may be readily followed from Table XI. 

As the purpose of these calculations is restricted to setting forth limitations and 
imparting ideas of the general magnitude of the quantities involved, it would be out 

44 



















































For a run of 2 miles between stops, at an average speed of BO miles per hove, this table sets forth the calculations oj the tractive force {/./'.) paver and energy at the 
axles per ton weii/ht of train for a 200-ton train at various rates of acceleration, the bruiting giving a rate of retardation equal to the rdtc of acceleration. 


THE TRACTIVE FORCE AND POWER AT THE 






































ELECTRIC RAILWAY ENGINEERING 


of place to employ any close degree of accuracy ; thus but three, and often only two, 
significant figures are employed. 

In Table XI., by expressions such as “ energy expended at the axles ” is meant 
the propelling energy alone. The braking energy expended in virtue of the 
stored-up energy of the train is, for low rates of acceleration, often a very large 
percentage of the total energy expended at the axles in propelling the train. A 
considerable portion of this may he recovered by “ regenerative control” methods. 



Fig. 41, Curves for Tramcar operated on Ordinary Series Parallel and on 

Regenerative Control Systems. 

Basis of calculations Weight, loaded car, 11 tons ; car friction, 19 lbs. per ton, excluding gearing ; motor efficiency, 

SO per cent., including gearing ; 5-sec. stops ; schedule speed, S miles per hour; level track. 

The amounts involved in the above case of an average speed of 30 miles per hour 
for a two-mile run from start to stop are shown in Table XII. 

Table XII. 


Recoverable energy per tun mile in percentage of total energy expended at axles 
per tico mile run from start to stop and average speed of 30 miles an hour. 


Rate of acceleration in miles per hour per second . 

I. 

0-50 

0-60 

1 *00 

1*40 

1-80 

2-20 

Maximum speed, i.e., speed at completion of accelera-) 
tion, in miles per hour . . . . . .) 

II. 

60 

48 

35 

33 

32 

31 

Stored-up energy of [In foot-pounds (3-P2 x IV. 2 ) 
motion per ton weight 1 of Table XI.) . . ( 

III. 

265,000 

136,000 

91,000 

80,600 

75,500 

71,000 

of train at above speed (In watt-hours (III. -h 2,650) 

IV. 

100 

51 

34 

30 

28‘5 

27 

Non - recoverable 
energy at axles 
in watt - hours 
per ton weight 
of train, i.e., ' 
energy wasted 
in inevitable 
friction . 

'For accelerating interval (XVII. 1 
of Table XI. minus IV. of :>- 
Table XII.) . . . . 1 

For constant speed interval) 
(XVII1. of Table XI.) .[ 

V. 

VI. 

18 

0 

5 

25 

2 

28 

1-1 

28 

0-9 

28 

0-6 

28 

For retarding interval (same as V.) 
Total of non-recoverable energy! 
for 2-mile run from start to [■ 

VII. 

VIII. 

IS 

36 

5 

35 

2 

32 

11 

30 

0-9 

30 

0-6 

29 

l stop (V. + VI. + VII.) . J 








lotal non-recoverable energy in watt-hours per ton-) 
mile (VIII. 4-2).j 

IX. 

18 

17 

16 

15 

15 

14 

Recoverable energy in watt-hours per ton (IV. - VII.) 

X. 

82 

46 

32 

29 

276 

26-4 


,, per ton-mile (X.-t-2) 

XI. 

41 

23 

16 

15 

14 

13 

Watt-hours expended at axles per ton-mile (IX.-f-XI.) 
Recoverable energy per ton-mile in percentage of 1 

XII. 

59 

40 

32 

30 

29 

27 

energy expended at axles, i.e. (XI. in per cent. 1 

XIII. 

70% 

58% 

50% 

50% 

49% 

48% 

of XII.). 

. 





46 






































































THE TRACTIVE FORCE AND POWER AT THE AXLES 

Item XIII. of Table XII. gives the percentage of recoverable energy; this only 
lepiesents the recovered energy on the basis of 100 per cent, efficiency of recovery. 
Of couise, the recovery will be at far less than 100 per cent, efficiency, for the motors 
must act as dynamos with very variable speed and load, and there will be external waste 
in controlling the rate of regenerative braking. Assuming that the energy required 
from the trolley or third rail averages L83 times the energy expended at the axles in 
propelling the train, and that the stored energy is recovered at 66‘7 per cent, efficiency, 
then the percentages of recovered energy for the case analysed in Tables XI. and XII. 
are as set forth in Table XIII. 


Table XIII. 


Summary of results given in Table XII. 

Assumptions are— 

Energy input = P33 x energy at axles. 1 

Mean efficiency of recovery by regenerative braking = 66*7 per cent. 


Rate of 
Acceleration 
in Miles 
per Hour per 
Second. 

Energy Input 
to Train in 
Watt-hours per 
Ton-mile 
(1-33 x XII. 
of Table XII.). 

Energy recovered 
by Regenerative 
Braking in Watt- 
hours per Ton- 
mile (0'(>07 of XI. 
of Table XII.). 

Percentage of 
Energy 
recovered to 
Energy Input 
to Train. 

0'50 

79 

27 

34% 

0-60 

53 

15*3 

29% 

TOO 

43 

10-7 

25% 

T40 

40 

10-0 

25% 

1-80 

38 

9*4 

25% 

2-20 

36 

8-7 

24% 


Thus by means of reconverting to electrical energy for return to the line, we may, 
in the above case, recover some 25 per cent, of the energy input to the train. Of 
course, this percentage varies greatly, depending 
chiefly upon the frequency of stops and the 
schedule speed between stops. In the case of 
tramway work, it is also greater in a hilly 
district. TV hile these articles relate to heavy 
electric traction, it will nevertheless be of 
interest to give curves based on results obtained 
in the authors’ practice from comparative tests 
made by them upon tramcars equipped on the 
regenerative control principle and on the ordi¬ 
nary series-parallel control system. These 
curves are reproduced in Figs. 41 and 42. 



From the curves one sees that for relatively 
1ow t schedule speeds and infrequent stops the 
advantage of employing regenerative control 
becomes very slight; and taking into account 
the greater weight of a regenerative control 
equipment, the use of such a system would, in 
certain cases, even be a distinct disadvantage. 

On the other hand, a relatively high schedule speed, with frequent stops, permits 


Different Speeds on Level Track. 

Basis for calculationFour stops per mile; car 
weight, loaded, 11 tons ; car friction, 19 lbs. per 
ton ; motor efficiency, SO per cent.; 5-sec. stops. 


1 This value will vary considerably with the type of equipment, the rate of acceleration, the schedule 
speed, and the number of stops per mile, and is only taken as a rough value for illustrative purposes. 


47 















































ELECTRIC RAILWAY ENGINEERING 


of much greater advantages from the use of a regenerative control system than 
is generally realised. In fact, the brief periods of notoriety which these systems 
enjoy, prior to disappearing from the scene, appear to be in considerable 
measure attributable to the failure to make exhaustive comparative tests of a 
character suitable to bring out clearly the considerable advantages which such 
systems would possess for certain cases. In view of the large amount that is 
written on this subject of regenerative control, the absence of a thorough recognition 


30 Miles per Hour. 
A 


45 Miles per Hour. 
B 


oy rules 


per nour. 

C 


■I 8 
■Sk 


IB 

W5 




X -lJ 

| a 


z-4 

20 

1(5 

12 

•8 

•4 









IV 

: II 

11 






I | 







: 1 







: \ 

; \ 

! \ 







• V 

; 














36 

3^ 

28 

24 

20 

l6 

12 

8 

4 




















































11 


— 





\ 

V w ^ 

v*** 






IV 







0 4 *8 12 1-6 20 .24 
Rate or acceleration in 
miles per hour per second. 


2-4 

2-0 

1-6 

1-2 

•8 

*4 


o 20 60 100 

watt-hours at axles per ton mile. 

0 




3''. 

1 

n 






i 

\ 





VIII 

\ 

1 

\ 

* 

\ 





\ 

\ 


\ 





i 

i 





- 


\ 

\ 














24 

2-0 

1-6 

1-2 

•8 

•4 





IV 






VIII 

l 







\ 

\ 







\ 

\ 







\ 








k 

% 












0 20 60 100 0 20 00 100 

Watt hours at axles per ton mile, watt-hours ataxies per ton mile 


3^ 

32 

28 

24 

20 

16 

12 

8 

4 

























II, 



✓ 

/,* 

/. 

V 




\ 

V 

_ 

s 

//* 











iy,*- 

,/ 

• / 

/ 





VIII 

/ 

/' 




















36 

32 

28 

24 

20 

16 

12 

8 


0 4 -8 1-2 1-6 20 24 
Rate of acceleration in 
miles per hour per second. 


















IV 



■/ 

/* 






* / 

/ 






/ 

/' 





VIII 

✓ 

/ 

































0 4 -8 1-2 1(5 20 24 

Rate of acceleration in 
miles per hour per second. 


Fig. 43. Curves of Energy and Maximum Instantaneous Power at Axles. 

Curves numbered I = One-mile run from start to stop. 

» II = Two-mile „ „ „ 

,, ,, IV = Four-mile ,, „ „ 

„ „ VIII = Eiglit-mile „ „ „ 


of the real conditions of success or failure forces the authors to conclude that their 
inventors, or rather the exploiters and their technical staff, have not themselves yet 
arrived at a clear understanding of the matter. 

There is another simple means of reducing the energy input to a certain extent. 
This consists in “ drifting ” or “ coasting” to the destination, and decreasing the use 
of brakes, or, in other words, employing the train friction to brake the train. This 
has already been alluded to on pp. 23 and 27. The method of operation reduces the 
energy required at the axles, since the train friction is unavoidable, and might as well 
be employed to reduce the amount of energy required to be stored up in the train, 

48 ' 



































































































THE TRACTIVE FORCE AND POWER AT THE AXLES 

only to be subsequently wasted at the brake shoes. By modifying the diagrams to 
take into account the further economy obtainable by substituting a “drifting” stage 
for the constant speed stage, a moderate reduction may be effected in the watt-hours 
per ton-mile for very short runs between stops, for the higher rates of acceleration; 
but for longer runs between stops the result will be relatively but slightly affected. 
This is also true of the economy attending “ acceleration on the motor curve,” a 
discussion of which must be deferred. The use of diagrams based on constant speed 
running and equal rates of acceleration and retardation has the advantage of giving a 
better-defined basis for comparison of operation under various conditions as regards 
schedule speed, frequency of stops, and accelerating rate ; it gives results on the safe 
side of the attainable values. The magnitude of the errors introduced by not taking 
advantage in these calculations of the further economies of “ drifting” and of 



WaCC Hours &C fh/es per Tor Hl/Te, for £00 To n Tra/n 

Fig. 44. Curves of Energy required at Axles of 200-Ton Train for various 
Lengths of Run and Schedule Speeds. 

Assumed mean rate of acceleration and braking = I mile per hour per second; level track 


acceleration on the motor curve, will be discussed in a later section. “Drifting ” has 
the advantage over regeneration that one avoids the loss of energy involved in recon¬ 
verting mechanical into electrical energy. Advantage ought to be taken, according to 
the conditions, of both of these means of securing increased economy. 

Calculations on the same lines as those set forth in Table XI. have been 
made for other speeds and frequency of stops, but it will only be practicable to 
give the final results as plotted in curves. In the upper row of curves of Fig. 48 
is given the energy required at the axles in watt-hours per ton-mile corresponding 
to various rates of acceleration and to schedule speeds of 80, 45, and 60 miles 
per hour between stops, and for 1, 2, 4, and 8-mile runs. 

In the lower row of curves of Fig. 43 are given, for these same conditions, 
the values of the maximum instantaneous power at the axles in kilowatts per ton 
weight of train. 

E.R.E. 


49 


E 






























































ELECTRIC RAILWAY ENGINEERING 

Working from the curves in the upper row of Fig. 43, and limiting the 
investigation to a mean rate of accelerating and braking equal to 1 mile per hour 
per second, the full line curves of Fig. 44 are obtained. These curves, for which 



8 


A 


2 



V) 

<3 

v 



>3 





halt Hours Input Co 7r*inpcrTonMile,for &)0-Ton 77*in 

Fig. 45. Curves of Energy Input to 200-Ton Train for various Lengths of Run and 

Schedule Speeds. 

Assumed mean rate of acceleration and braking = 1 mile per hour per second ; level track. 


the stops are taken as of 
speed and watt-hours at 



o -8 1-6 24 

Fig. 46. Curve showing Rela¬ 
tion BETWEEN THE ACCELERAT¬ 
ING Rate and the Ratio of 
the Maximum to the Average 
Power at the Axles. 200-Ton 
Train operated with One 
Stop per Two Miles, at an 
Average Speed of 30 Miles 
per Hour between Stops. 

length of run from start 


15 seconds duration, show the relation between schedule 
axles per ton-mile for a 200-ton train. For lighter 
trains the energy required at the axles per ton-mile 
would be slightly greater, and vice versa for heavier 
trains. 

With a view to obtaining corresponding values 
for the total input to the car, the efficienc} 7 assumptions 
indicated by the dotted lines of Fig. 44 have been 
made. These efficiencies are taken lower the more 
severe the service, the degree of severity of the service 
being indicated by the extent to which a curve at the 
point under consideration has approached the horizontal 
direction. In general the service is more severe the 
more fiequent the stops for a given schedule speed, 
or the greater the schedule speed for a given frequency 
of stops. The more severe the service the greater is 
the length of time that rheostatic losses are occurring. 
The efficiency curves are only rough approximations, 
and may be considered as giving a general idea of 
the values obtaining in series-parallel control with 
600-volt trolley pressure and continuous-current 
motors. 

The results for the watt-hours input to the train 
per ton-mile as a function of the schedule speed and 
to stop, are, for 15-second stops, given in the curves 
50 

























































































THE TRACTIVE FORCE AND POWER AT THE AXLES 

of Fig. 45 for a 200-ton train, the mean rate of acceleration and braking being 
taken at 1 mile per hour per second. 

Item XXII. of Table XI. shows the dependence upon the accelerating rate 
of the maximum to the average power at the axles for the 2-mile run at an 
average speed of 30 miles per hour. The values are plotted in the curve of 
Fig. 46. Here we see plainly one of the disadvantages of a high rate of 
acceleration. It entails equipments of high maximum capacity, and also power¬ 
house plant and line with high maximum capacity. The larger the number of 
equipments in service, the more will the disadvantages of a high ratio of maximum to 
average capacity be decreased, since the peaks of load of the different equipments 
will be so distributed as to give, at the power-house, a far lower value for the 
ratio of maximum to average load. Herein lies one of the great advantages of 
electric traction ; for while, for such a service as that corresponding to the curve 
of Fig. 46, a steam locomotive would be obliged to provide energy at the axles 



Fig. 47. Typical Train Characteristic (S.-T.) Curves for Trains operated 

by Continuous Current. 


at rates constantly varying through a wide range, an electric service, with 
numerous trains fed from a single power-lwuse, would give a relatively constant 
load on the prime movers at the power-house, and such a number of sets may at 
any time be placed in service as shall suffice to ensure operation at an economical 
range of loads. 

Again, another reason for operating at low accelerating rates in steam service, 
is seen from Fig. 46. Were a steam road to operate trains at a schedule speed 
of 30 miles an hour between stops, and with one stop every 2 miles, the moderate 
rate of acceleration of 1*4 miles per hour per second would give a ratio of maximum 
to average load at axles of over 10:1, and would entail very low economy at the 
locomotive. Somewhat higher rates of acceleration than this, and consequently 
higher schedule speeds, can, however, generally be economically provided for by 
electrical operation where a frequent service is employed, since the peaks 
occasioned by each of the numerous trains will occur at different times, resulting 
in a relatively uniform load on the engines at the power-house, and thus 

cr E 2 



































Fig. 


48. Typical Train Characteristic (3.-T.) Curves for Continuous Current Equipments. 




52 









































































































































































































































































































































































































































THE TRACTIVE FORCE AND POWER AT THE AXLES 


permitting of far smaller total steam engine capacity than the sum of the maximum 
capacities of the numerous locomotives which would be required with a steam 
locomotive service. 

In a recent paper (“ Technical Considerations in Electric Ptailway Engineering,” 
Institution of Electrical Engineers, January 25th, 1906), Carter has published the 
curves reproduced in Fig. 47, which show typical speed-time curves for trains 
operated by continuous current. Carter acknowledges that credit is due to 
Mr. E. H. Anderson for first pointing out this use of a single curve for a number 
of runs. As it will appeal to many engineers as more useful in rapid work, the 
authors have developed from Carter’s curves, as shown in Fig. 47, the chart 
of curves given in Fig. 48. 


53 


Chapter IV 

THE STUDY OF THE CHARACTERISTICS OF ELECTRIC RAILWAY 
MOTORS AND OF SECTION CHARACTERISTICS AND THE CON¬ 
STRUCTION OF LOAD CURVES 

I N the vast majority of electric traction undertakings, the continuous-current series 
motor is employed. A considerable range of variation is possible in the design 
of this type of motor; the feature which chiefly affects the form of the speed-time curve 
during the accelerating interval is the degree of saturation of the magnetic circuit. 

In the series motor, the field excitation is supplied by the main current, which 
passes not only through the armature windings, hut also through the field magnet 
windings on its way from the trolley or third rail to the track rails or other return 
conductor. The excitation is consequently proportional to the input to the motor, 
and hence also roughly proportional to the load on the motor, and were it not for 
the saturation of the magnetic circuit and for the internal resistance drop, the speed 
at constant terminal voltage would be inversely proportional to the amperes input, as 
shown in curve A of Fig. 49, where, for instance, at 50 per cent, of full load, the speed 
is double that at full load. In other words, letting I = current input, and letting 
R.P.M. = speed in revolutions per minute, then, assuming 100 per cent, efficiency 
and no saturation of the magnetic circuit, we should have for all inputs 

I X R.P.M. = constant. 

Thus curve A of Fig. 49 represents the limiting case with decreasing saturation. 
Now, the other limiting case would be met in a motor with a magnetic circuit 
reaching complete saturation with an infinitely small current, and incapable of 
transmitting an increased magnetic flux with increasing current. Obviously, with such 
a motor, the speed (neglecting the internal I.R. drop) would, for constant terminal 
voltage, be constant for all loads. The horizontal line B of Fig. 49 is the speed 
curve for this limiting case. This latter is, in practice, an utterly unapproachable 
limit; nevertheless the series motors in most extensive use are designed with a highly 
saturated magnetic circuit at full load current. For a representative motor we shall 
take the G.E. 66 A., of which over a couple of hundred are in use on the Central 
London Railway and the Great Northern and City Railway, and many hundreds 
more on the elevated and underground railways of New York and other American 
and Continental cities, as well as on the North-Eastern Railway in this country. 
Some of the characteristic curves of this motor are reproduced in Fig. 50. These 
curves are based on the employment of a gear reduction of 71 to 18 (or a ratio of 
3‘94), and on a wheel diameter of 34 ins. For our present purpose we wish to 
express the speed in terms of the percentage speed at rated full load, and use as 

54 


CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 


absciss® the percentage of the output at rated full load. We must digress for the 
moment to explain the basis of the nominal rating employed for railway motors. 

An arbitrary basis of rating for railway motors, which has now been in generally 
accepted use for a number of years, defines the nominal capacity as the horse-power 
output, causing 75 degrees Cent, thermometrically determined temperature rise of 
the hottest accessible part after 1 hour’s continuous run on a testing stand at 
rated voltage. Railway motors in actual service are required to carry an average 



load of only some 25 per cent, or less of their rated load, and this shows the great 
importance of designing them for high efficiency at light loads. 1 Moreover, they are 
inherently capable of being proportioned to give this result, for the loss in field 
excitation, instead of being, as in shunt motors, a component of the “no load” loss, 
increases from a negligibly small amount at no load, with the square of the load, and 
hence is a component of the so-called “ variable losses.” In motors for light work, 
however, the gearing loss comes in and increases the “ no load ” losses considerably ; 
but large, direct-connected series motors are inherently of very high efficiency at light 

1 “ The continuous capacity of railway motors (/.e., the load they can take continuously) may be 
taken as approximately one-fourth of the commercial rating.”—Carter, “ Some Notes on High-speed 
Electric Railway Work” (paper read before the Rugby Engineering Society December 1st, 1904). 

55 












































Foa nds ~Tr&ct>i \fe 


ELECTRIC RAILWAY ENGINEERING 

loads. These considerations have reference exclusively to motors and gearing; but 
it should be kept in mind that series motors require auxiliary controlling apparatus 
in which, when starting, very considerable losses take place in external resistances 


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200 220 240 260 200 


Fig. 50. Curves showing Efficiency, Speed, and Tractive Force of Gr.E. 66 A. Motor 

of 125 H.-P. rated Output. 


for continuous-current motors, and in transformers and potential regulators for 
alternating current motors. 

The G.E. 66 A. is rated at 125 h.-p. From Fig. 50 we see that its efficiency in the 
neighbourhood of this load is about 90 per cent. The curves relate to its performance 
with 500 volts at its terminals. Hence the amperes input at rated load— 

125 X 746 _ 

— 0*90 X 500 — * j08 am P eres - 
56 

































































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 

The ordinate indicated by the broken line in Fig. 50 thus corresponds to the 
rated load. We find from the speed curve that, with the given gear ratio and wheel 
diameter, the corresponding speed is 14 miles per hour. 

14 m.p.h. = 14 X 5,280 = 74,000 ft. per hour = 74,000/60 = 1,230 ft. per minute. 
Car wheel diameter = 34 ins. 

Car wheel circumference = 34 X tt = 107 ins. = 8*92 ft. 

• Speed of car wheels at rated load of motors (i.e. 208 amperes per motor) 
= 1,230/8*92 = 138 r.p.m. 

.’. Speed of motors at rated load of 208 amperes per motor = 138 X 3*94 — 544 
r.p.m. 

By means of the slide rule one readily derives the values set forth in Table XIV. 


Table XIY. 

G.E. 66 A Railway Motor at 500 Volts. Ratio of gearing = 3*94. Diameter of car 

wheels = 34 ins. 


Amperes input 

260 

208 

160 

120 

80 

40 

30 

21 

Watts input .... 

130,000 

104,000 

80,000 

60,000 

40,000 

20,000 

15,000 

10,500 

Per cent, efficiency 

88 

90 

90 

89 

85 

70 

50 


Watts output 

114,000 

93,500 

72,000 

53,400 

34,000 

14,000 

7,500 

_ 

Horse-power output 

153 

125 

96-5 

71-5 

45-5 

18-8 

10-1 

_ 

Per cent, of rated load . 

122 

100 

77-2 

57-3 

36-4 

15-0 

8-3 

_ 

Speed train in miles per hour 
Speed motors in revolutions 

12-8 

14-0 

15-5 

17-5 

22-5 

39-0 


-- 

per minute 

Speed motors in per cent, of 

497 

544 

601 

680 

874 

1,510 

— 

— 

full load speed . 

91*5% 

100% 

110-5% 

125% 

161% 

278% 

— 

— 


From the results in Table XIY. the full line curve of Fig. 51 has been drawn. The 
two broken lines in Fig. 51 represent the limits for no saturation and absolute saturation 
respectively. These have merely been transferred from Fig. 49. 

The latest type of train on the Central London Railway comprises two motor cars 
and five trailer cars, the motor cars being at the opposite ends of the train. The 
motor cars weigh 23 tons each, and the trailers weigh 13*5 tons each. The total 
seating capacity of the train is for 324 passengers, or 2*85 passengers per ton of 
unloaded train. Taking an average load factor of 25 per cent, during the period of 
service of the train, we have an average of 81 passengers per train, or a live load of 
(81 x 140)/2200 = 5*15 metric tons, thus giving for the weight of train with average 
load— 

Motor cars = 2 x 23 = 46*0 tons, 

Trailers = 5 x 13*5 = 67*5 tons, 


Passengers = 


81 x 140 
2200 


5*2 tons, 


118*7 tons, 

or, say, 120 tons for the total train weight. 

The motor equipment is made up of two G.E. 66 A. motors on each of the two 
motor cars, or a total of four G.E. 66 A. motors per train of 120 tons. As the curves 
of Fig. 50 relate to one G.E. 66 A. motor, it will be convenient to derive from them 
other data for the total tractive force and total input to the motors. For the present 

57 




















ELECTRIC RAILWAY ENGINEERING 


the losses in the controlling rheostats will be neglected. In actual practice the 
motors are, at the moment of starting, connected two in series and two in parallel; 
and, after the acceleration is about half completed, all four motors are thrown in 



F&rcenO of Pasted Load 

Fig. 51. To explain Connection between Speed and Input of G.E. 66 A. Motor. 


parallel. This method of operation by “ series-parallel control ” reduces the rheostat 
loss. But for the purpose of explaining the points under immediate consideration, we 
shall first assume that all four motors are in parallel from the moment of starting. 
The four motors develop 4 X 125 = 500 h.-p. at 4 X 208 = 882 amperes input when 

58 




























































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 

the terminal pressure is 500 volts. With 34-in. wheels and a gear ratio of 3’94, this 
corresponds to a speed of 14’0 miles per hour, or 

(14‘0 X 5280) / 60 = 1,230 ft. per minute. 

The output in foot-pounds per minute = 500 X 33,000 = 16,500,000. 

Hence the tractive force at full load is 

16,500,000/1230 = 13,400 lbs., 
or 13,400/832 = 16*1 lbs. per ampere at 500 amperes. 

For a motor with constant efficiency at all loads and with constant speed (as 
represented by curve B of Fig. 49), the tractive force per ampere would be a constant 
for all values of the current; for a motor with constant efficiency at all loads, but with 
the speed curve A of Fig. 49, i.e., for a motor with no saturation of the magnetic 
circuit, the tractive force per ampere would be proportional to the current; for the 
practical case of the G.E. 66 A. motor, the tractive force would vary at an intermediate 
rate. The tractive force per ampere for this last case is worked out in Table XV., the 
curves of Fig. 50 serving as the basis for the calculations. 


Table XV. 

Four G.E. 66 A. Railway Motors. Ratio of gearing = 3’94. Diameter of car wheels 

= 34 ins. All four motors in parallel. 


Amperes input per 







30 


motor 

Amperes input for four 

200 

208 

160 

120 

80 

- 

40 

21 

84 

motors 

1,040 

832 

640 

480 

320 

160 

120 

Speed train in miles per 









hour .... 

12-8 

14-0 

15*5 

17*5 

225 

390 

— 

— 

Speed train in feet per 






3,430 



minute 

1,126 

1,230 

1,363 

1,540 

1,980 

— 

— 

Kilowatt input at 500 








volts .... 

520 

416 

320 

240 

160 

80 

60 

42 

Efficiency at 500 volts . 

88 

90 

90 

89 

85 

70 

50 

— 

Kilowatt output at 500 









volts .... 
Horse-power output at 

457 

374 

288 

214 

136 

50 

30 

40-2 


500 volts . 

Output in foot-pounds 

613 

500 

386 

287 

182 

75'0 


per minute 

20,200,000 

16,600,000 

12,700,000 

9,460,000 

6,000,000 

2,480,000 

1,330,000 

— 

Tractive force in pounds 

17,900 

13,500 

9,300 

6,150 

3,030 

725 

— 

— 

Tractive force in pounds 






453 



per ampere 1 

17-2 

16T 

14-5 

12-8 

9-46 




1 These values are approximately proportional to the flux. 

The results are plotted in the full line curve of Fig. 52, together with the limiting 
curves for equivalent motors with increasing and decreasing saturation of the magnetic 
circuit. 

Assuming constant internal losses in a series motor, the tractive force exeited 
will be precisely the same for a given current through the motor, whethei the motoi 
be at rest or running at any speed. Now we shall introduce but slight inaccuracy by 
neglecting the difference in the internal losses, and we are thus enabled to deduce the 
initial accelerating rate which we may obtain with any current. This is done in 
Table XYI. 


59 


















ELECTRIC RAILWAY ENGINEERING 


Table XYI. 

Four G.E. 66 A. Railway Motors. Ratio of gearing = 3’94. Diameter of car wheels 

= 34 ins. All four motors in parallel. 


Amperes input per train 

1,040 

832 

640 

480 

320 

160 

120 

84 

Tractive force in pounds 

,, ,, ,, per ton weight 

17,900 

13,500 

9,300 

6,150 

3,030 

725 

— 

0 

of train 

Initial rate of acceleration in miles per 
hour per second, neglecting the train 

149 

112-5 

77'5 

51-2 

25-2 

6-1 


0 

resistance at very low speeds . 

1-49 

1-13 

0-775 

0-512 

0-252 

0-061 

— 

0 


Curve I. in Fig. 53 is plotted with ordinates equal to the tractive force per ton 
weight of train, and with abscissae equal to the amperes input with all four motors in 


74 

















































Tractive Force In Pounds per Ampere 




























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Amperes Input to Four Motors in Parallel 

Fig. 52. To explain Connection between Tractive Force and Input, using Four G.E. 

66 A. Motors. 

6o 





























































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 


parallel. This same curve, owing to a purely accidental coincidence resulting from 
the particular system of units we have employed in these articles, might also be read, 
as indicated in the figure, to ordinates expressing the initial acceleration in miles per 
hour per second, provided that the train resistance could, at very low speeds, be 
neglected. From Fig. 6 (on p. 9) we find, however, that the train resistance at 
low speeds amounts to some 6 lbs. per ton. Hence curve II. has been added on 
Fig. 58, with ordinates reduced by 6 lbs. below the corresponding points of curve I. 



Fig. 53. To explain Connection between Tractive Force (Curve I.), Initial 
ACCELERATING RATE (CURVE II.) AND INPUT, USING FOUR G.E. 66 A. MOTORS. 


Now, suppose we wish to operate one of these Central London trains with a 
constant rate of acceleration of 1 mile per hour per second. When the train is at rest, 
we shall require such a resistance in the circuit as to permit the 500 terminal volts 
to send in 800 amperes. Obviously we shall require 500/800 = 0*625 ohm in the 
circuit. Two factors would enter to reduce the amount of resistance required at the 
first instant. The first factor is the inductance of the motors (chiefly in the field 
windings), and of the apparatus and lines through which these derive their supply. 
The second factor is the great resistance of the train when at rest, which makes it 
necessary, for the first instant, to have a much heavier current to obtain the desired 

6i 














































ELECTRIC RAILWAY ENGINEERING 


initial acceleration of 1 mile per hour per second. We can, however, neglect these 
two figures for the present investigation ; we shall, therefore, assume that the train 
starts as calculated, with an acceleration of 1 mile per hour per second. But imme¬ 
diately the motors begin to gain speed, they generate a counter-electromotive force 
which will reduce the voltage across the external resistance, and hence also the current 
and the accelerating rate, until a section of the rheostat is cut out. The accelerating 
rate may thus be restored and maintained at the original value, by successively cutting 
out sections of the starting rheostats. Suppose that when the last section of external 
resistance is cut out, the motors are running at a speed corresponding to but 470 volts 
counter-electromotive force. At first a current will flow equal to {(500—470)/internal 
resistance of motors} ; but this will gradually be reduced by the increasing counter¬ 
electromotive force of the motors, and the current will gradually fall, approaching as a 
limit the value required to overcome the tractive resistance of the train at the 
corresponding speed. 

The subject of “acceleration on the motor curve” has occasioned a good deal of 
discussion, and should be considered with some care at this point. 

The internal resistance of the G.E. 66 A. motor at 75 degrees Cent, is equal to 013 
ohm. Resistance of four motors in parallel = 0‘13/4 = 0033 ohm. Suppose we wish, in 
the case of the standard Central London train, to have an initial acceleration of 1 mile per 
hour per second. We have already seen that, neglecting the reactance of the circuits and 
the higher resistance of the train when at rest, we should require a resistance of 500/800 
= 0‘625 ohm; and of this the resistance external to the motors would be 0‘625—0‘033 
= O’59 ohm. The current flowing from the line at the instant of closing the circuit will 
be 800 amperes. Let us, as an approximation, consider successive intervals of LO second 
each. For the first ten of these intervals let us leave the external resistance unchanged. 
At the end of 1 second the speed of the train will be nearly 1 mile per hour; it will not 
be quite 1 mile per hour, for, as we are about to ascertain, the current, and hence 
the accelerating rate, will decrease during the course of the 1 second interval. Let 
us take it, however, at approximately 1 mile per hour. From Fig. 50 we find that with 
a current of 800/4 = 200 amperes per motor, the constant speed of the motor is 14 miles 
per hour when operated with 500 volts across its terminals. Its counter-electromotive 
force is then 500—200 x 0‘13 = 500—26 = 474 volts. Hence, with the same current 
strength of 200 amperes per motor, the counter-electromotive force at a speed of 1 mile 
per hour will be (1/14) x 474 = 33‘8 volts. 

Hence the current input to the four motors in parallel will, at the end of 1 
second, be equal to (500 — 33’8)/0’625 = 745 amperes. 

For this current strength, we find from curve II. of Fig. 53 that the accelerating- 
rate is only 0 - 90 miles per hour per second. Hence the mean acceleration for the first 
second will be but (LOO -f- 0*90)/2 = 0'95 mile per hour per second. Were this main¬ 
tained during the following second, the speed at the end of 2 seconds would be 1*90 
miles per hour, the counter-electromotive force would be 1*9 X (474/14) = 64 volts, 
and the current input to the four motors in parallel would be (500 — 64)/0'625 = 697 
amperes. 

The smaller the component intervals for which we make the calculations, the more 
correct will be the result. Making precise calculations by the less elementary but more 
exact method (described in the note on p. 63), for the first 10 seconds during which 
the external resistance is maintained constant at 0’59 ohm, we obtain values from 
which the curves of Figs. 54, 55, and 56 have been plotted. It is evident that the 
mean acceleration for the first 10 seconds is only 0‘69 mile per hour per second. At 

62 



Figs. 54 to 59. Acceleration-Current-Speed-Ti.me Curves for Four G.E. 66 A. Motors in Parallel. 



















































































































































































































■ 
























































































































































































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 

the end of 10 seconds, the speed is 6*9 miles per hour. Let us now reduce the resistance 
in the motor circuit to such a value that the acceleration is restored to its original 
value of 1 mile per hour per second. This must be such a resistance as shall bring 
the current again up to its original value of 800 amperes. At a speed of 6*9 miles 
per hour, this latter current produces a counter-electromotive force of 38-8 X 6*9 = 234 
volts ; the voltage drop in the resistance must therefore be 500 — 234 = 266 volts, 
and the resistance =266/800 = 0*333 ohm, corresponding to an external resistance 
of 0-333 — 0-033 = 0*30 ohm. 

From Figs. 57, 58 and 59, we see that, during the next 10 seconds, the accelera¬ 
tion decreases from 1*0 mile per hour per second to 0-39 mile per hour per second, 
the current input decreases from 800 amperes to 450 amperes, and the speed increases 
from 6 - 9 miles per hour to 13-1 miles per hour ; the mean acceleration during the 
second step (10 to 20 seconds) is therefore 0'62 mile per hour per second. Let us now 
again cut out the external resistance in order to bring the acceleration up to its original 
value. We find, by the method which we employed for the second stage, that the 
resistance in the motor circuit for the third stage 

500 — 33-8 X 13-1 500 - 443 57 , 

— 800 ~ 800 _ 800 ~ °' 071 0 im; 
therefore the external resistance = 0*071 — 0-033 = 0*038 ohm. 

The results of employing this resistance in circuit during the following seconds 
are shown in the third sections of Figs. 57, 58, and 59. The speed is now 18*5 miles 
per hour, the average acceleration during the third step being 0*54 mile per hour 
per second, and the average acceleration during the total 30 seconds from the start 
= 0*62 mile per hour per second. 

Knowing, as we now do from the curves of Fig. 57, that the rate of acceleration 
will fluctuate more widely at each succeeding 10-second interval, we draw the con¬ 
clusion, borne out in practice, that the interval of running on each successive step 
should be decreased. Thus, if we worked between the limits of 800 amperes and 500 
amperes, the first three intervals would be (roughly) 10, 7, and 6 seconds; this 
would obviously affect the subdivision required in the rheostats. The matter is very 
complicated, and is rendered still more so by the customary practice of operating with 
“ series parallel ” control, to which we shall shortly give our attention. 

The main point to which we here wish to draw attention is, that the whole accelerating 
interval is made up of sections, during each of which we are “ running on the motor 
characteristic,” except in so far as the motor characteristic is modified hg a resistance of 
constant value in series with the internal resistance of the motor. 


Note on the Exact Method used in obtaining Figs. 54 to 59. 

The exact method, essentially a graphical one, consists in deriving a relation 
between speed and acceleration. For that purpose, in Fig. 60 the current inputs have 
been taken as abscissae. As ordinates have been plotted— 

(1) The tractive force in pounds per ton (taken from Fig. 53); 

(2) The speed in miles per hour, corresponding to the current input and to the 

resistance in the motor circuit. 

In Fig. 60, 0*625 ohm has been taken as total resistance. The internal voltage 
would be (500 — 0-625 I.), while for the speed curve given in Fig. 50 the internal 
voltage for the same current would be (500 — 0‘033 I.). 

63 





ELECTRIC RAILWAY ENGINEERING 


To obtain the speed curve in Fig. 60, it has merely been necessary to calculate 
the ratio 

500 - 0-625 I. 

500 — 0-033 I. 

for various currents, and to multiply the speed given in Fig. 50 by this ratio. 

From Fig. 60, curve I. of Fig. 61 may be plotted, with speeds as abscissae and 
tractive forces as ordinates. The train resistance is plotted as a function of the speed 
in curve II. of Fig. 61 ; and the difference between curve I. and curve II. equals that 
part of the tractive force directly available for acceleration. As a tractive force of 



Current Inyout toFour /VJotors in far?)IleJ 

Fig. 60. Characteristic Curves of Parallel Operation of Four G.E. 66 A. Motors. 

100 lbs. per ton produces an acceleration of 1 mile per hour per second, the required 
relation between speed and acceleration has thus been found. For clearness, this has 
been plotted again in Fig. 62. In Fig. 63, a curve has been plotted with time in 
seconds as abscissae, and speed in miles per hour as ordinates. This latter curve is 
derived from the curve in Fig. 62, since we know that the tangent to the speed-time 
curve in Fig. 68 is proportional to the corresponding value of the acceleration in the 
curve in Fig. 62. 

The method, as described above, can be used for any resistance, and in case it is 
desired to calculate a total set of resistances, a great many interesting relations may 
be found between the different curves representing the various resistances. 

Without going into the details of the calculation, which would be on the lines 
already set forth in the previous example, we give in Figs. 61, 65, and 66 a set of 

64 


















































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 


curves (corresponding to those of Figs. 57, 58, and 59) for a mean acceleration of 
1 mile per hour per second, in which, instead of maintaining constant time intervals 
per step, we work between a maximum of 930 amperes and a minimum of 690 amperes 



Fig. 61 . Characteristic Curves of Parallel Operation of Four G.E. 66 A Motors. 


input to the four motors in parallel on each step. This accelerating rate is maintained 
until a speed of 13‘4 miles per hour is attained. The resistance per controller point 
and the number of seconds duration of run on each point are set forth in Table XVII. 

Table XVII. 

Controller Positions for Four G.E. 66 A Motors. Mean acceleration = 1 mile 
per hour per second. Speed = 13’4 miles per hour. 


Controller 

Point. 

Time in Seconds on 
each Point. 

Resistance in Series with 
Motors on each Point, in 
Ohms. 

1 

3-9 

0-50 

2 

3-2 

0*36 

3 

2*6 

0'24 

4 

2-1 

0-14 

5 

1-6 

0-064 


13’4 seconds have now' elapsed since the current was thrown on. Let the 
movement to the sixth controller point consist in cutting out the remaining external 
resistance of 0’064 ohm, and let the motors continue to accelerate with only the 
E.R.E. 65 F 




















































ELECTRIC RAILWAY ENGINEERING 


internal resistance of the four motors in parallel, i.e., 0’033 olim, in circuit. T\ e are 
thus “ accelerating on the motor characteristic,” as it is generally described. Let us 
continue running on the motor characteristic for 85'6 seconds. The acceleration will 
gradually decrease, and at the end of 85‘6 seconds, which is 99 seconds from the time 
of starting, the acceleration will have decreased to only 0'06 mile per hour per second 
(see Fig. 67). At this point a speed of 28’A miles per hour will have been attained (see 
Fig. 69). Let the current now be cut off, and the train permitted to coast (or drift) 
for 41 seconds. The retardation during coasting will be due solely to the train friction. 
From Fig. 6 (on p. 9 of Chapter I.) we see that, at speeds of some 27 miles per hour the 
train friction of a 120-ton train has on the Central London Railway been determined 



Acceleration m Mlies per Hourper Second Time m Seconds 

Fig. 62. Fig. 63. 

Figs. 62 and 63. Characteristic Curves of Parallel Operation of Four G.E. 66 A Motors. 

as about 9 lbs. per ton. On p. 21 of Chapter II. the rule was given that on a level 
track a tractive force of 100 lbs. per ton, in addition to the force required to overcome 
the tractive resistance, imparts to a train an acceleration of 1 mile per hour per 
second. Hence it follows that a train friction of 9 lbs. per ton will produce a 
retardation of 0*09 mile per hour per second. Therefore, at the end of 41 seconds of 
coasting, the speed will have fallen by 41 X 0’09 = 3'7 miles per hour below the 
maximum speed of 28'4 miles per hour, or to 247 miles per hour. At the end of 
41 seconds of “drifting,” 140 seconds will have elapsed since starting. Let the brakes 
now be applied, and with a pressure sufficient to increase the total train friction to 
100 lbs. per ton. This will increase the rate of retardation to 1 mile per hour per 
second, and will bring the train to rest in 24 - 7 (say 25) seconds, or 165 seconds from 
the start. Now during the acceleration on the first five controller points, i.e., during 

66 































































Acceleration m M'lltsfitr Hour f,er Second 



Time in Seconds. 

Fig. 64. 




Figs. 64—66. Acceleration-Current-Speeij-Time Curves fur Four G.E. 66 A. Motors in Parallel 













































































































































































Fig. 


Fig. 


Fig. 



Fig. 


Figs. 67— 


70. Acceleration-Current-Speed-Distance-Time Curves for Four G.E. 66 A. Motors in Parallel. 







































































































































































































































































































































































































































































































































































































































































































































































































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 

the hist 13 4 seconds, we maintained a mean acceleration of 1 mile per hour per 
second. Hence, for this interval, the mean speed was 6'7 miles per hour, and 

13*4 

the distance covered was 6*7 X g"gQQ = 0*025 mile. During the 85*6 seconds of 

operation on the sixth controller point the speed increased at an ever slower rate, as 
is seen from the curve of Fig. 69, and the mean speed is readily seen from this 
curve to be 24*4 miles per hour. Hence the distance covered on the sixth 
controller point 

, 85-6 

= 24*4 X q n = 0*584 mile. 

3 ,b(J(J 

During “ drifting ” the mean speed is equal to 

28-4 + 24-7 

p-= 26*6 miles per hour, 

and the distance covered equals 

26*6 X ttwwk — 0*302 mile. 

3,600 

During braking the mean speed is 

24*7 

—g— = 12*4 miles per hour, 

and the distance covered is 

25 

12*4 x g gQQ = 0*086 mile. 

We have thus obtained the values set forth in Table XVIII. 


Table XVIII. 

Distance Covered during each Operation for run of One Mile. 


Operation. 

Time in 
Seconds. 

Mean Rate of 
Acceleration in 
Miles per Hour 
per Second. 

Mean Speed in 
Miles per Hour. 

Distan ce 
covered in 
Miles. 

Rheostatic acceleration ..... 

13-4 

+ 1-00 

0-7 

0025 

Acceleration on the motor curve 

85-6 

+0-18 

24 5 

0-584 

Drifting ........ 

410 

-009 

26-6 

0302 

Braking ........ 

25-0 

-1-00 

12-5 

0086 


Adding up the four items in the last column, we find that we have covered a distance 
of 1 mile (0*997 mile). Hence the average speed is equal to -Av- = 21*8 miles per 

1OD 


hour. The acceleration, the current, the speed, and the distance at each moment 
from start to stop are plotted in Figs. 67, 68, 69, and 70. 

From the values of the current in Fig. 68 and the constant terminal potential of 
500 volts we obtain the kilowatts gross input to the train at any instant. From the 
values of the resistance external to the motors at each step, which are given in 
Table XVII., and the corresponding values of the current which are obtained from 
Fig. 68, the kilowatts dissipated in the rheostats at any moment may be calculated. 
The kilowatts gross input to the train, the kilowatts dissipated in rheostats, and 
the kilowatts input to the four motors are plotted in the three curves of Fig. 71. 
The curve of input to the motors is repeated in Fig. 72, and there is also drawn the 
corresponding curve of output from the motors, i.e., of the energy finally delivered to 
the car wheels. This latter curve could also have been derived from the speed and 

67 F 2 


















ELECTRIC RAILWAY ENGINEERING 



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tractive force from instant 
to instant, and it has, as 
a matter of fact, been 
checked by this means. 
From the curve of gross 
energy consumption in 
Fig. 71 we find that the 
train has consumed 18,310 
kilowatt-seconds, or 5*10 
kilowatt-hours, in the 
1-mile run from start to 
stop, or 42‘2 watt-hours 
per ton-mile. From the 
curve of energy finally 
delivered to the axles in 
Fig. 72 we find that there 
has been required at the 
axles for the 1-mile run 
13,330 kilowatt-seconds, 
or 3*7 kilowatt-hours, or 
30'7 watt-hours per ton- 
mile. The efficiency from 
contact shoe to car wheels 
is therefore 72‘6 per cent, 
for this 1-mile run from 
start to stop. 

Now let us carry the 
calculations through for 
this same 120-ton train 
operating with one stop 
per mile at a schedule 
speed of 21'8 miles per 
hour, and with the 
assumption of constant 
acceleration and retarda¬ 
tion at the rate of 1 mile 
per hour per second, and 
with uniform speed opera¬ 
tion from completion of 
acceleration to commence¬ 
ment of retardation. In 
Figs. 73, 74, and 75 are 
given the speed, tractive 
force, and nett energy 
for this cycle of opera¬ 
tions with straight line 
acceleration and retarda¬ 
tion. The nett energy 
required at the car wheels 


68 





























































































































































































































































































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 


will be found, by integrating Fig. 75, to be 14,700 kilowatt-seconds, or 4*1 kilowatt- 
hours. These values are but slightly (11 per cent.) greater than those obtained with 
operation on the motor curve characteristic, confirming thereby, at least for this case, 
the admissibility of the assumption made in the earlier articles of this series. 

Table XIX. gives the watt-hours per ton-mile at the car wheels, and also the 
maximum energy at the car wheels in watts. 


Table XIX. 

Nett Energy at Car Wheel. Mean rate of acceleration = 1 mile per hour per second. 


Fig. 

Numbers. 

Method of Operation. 

Watt-hours per 
Ton-mile at Car 
Wheel. 

Maximum 
Energy at Car 
Wheel in Watts. 

Average Energy 
at Car Wheels 
from Start to 
Stop, in Ohms. 

Ratio of 
Maximum to 
Average Energy 
at Car Wheels. 

67 to 72 

Acceleration on the motor curve 

30-7 

440,000 

81,000 

5-45 

73 to 75 

Straight-line acceleration 

34-0 

680,000 

89,000 

765 


It is clear that the result for the maximum energy required, is considerably too 
high when derived from our diagrams with “ straight-line acceleration,” and this fact 
must often be taken into consideration in cases where the diagram is used, although, 
as we see, the error involved by not taking it into consideration, leaves us on the safe 
side. The “ diversity factor ” in train operation, obscures the significance of absolute 
values for the “ ratio of maximum to average energy at car wdieels.” The important 
point is to realise that this ratio is so large a figure as 6 or thereabouts, in such a 
case, and that it would be considerably larger were it not for the decrease effected by 
accelerating on the motor curve. 

In the example of motor control which w T e have worked out above in considerable 
detail, we have assumed a case where the four motors are in parallel during the entire 
accelerating interval. It is, however, almost universal practice, where four continuous- 
current railway motors constitute a single equipment operated from a 500-volt circuit, 
to connect them, two in series and two in parallel, during the early portion of the accele¬ 
rating period. After the resistance in series with this series-parallel combination of 
the motors, has been gradually cut out, the four motors are all connected in parallel 
with one another, but at first in series with external resistance, which is again 
gradually cut out. To start the train with the same acceleration as for the parallel 
connections used in the curves of Figs. 67 to 72, the total resistance on the motor 
circuit would have to be double its former value; therefore 

2 X (external resistance of 0-50 ohms + motor resistance of 0"033 ohms) = 

F066 ohms. 

The internal resistance of the four motors in series-parallel (or briefly in 
“ series ”) connection is four times its former value, i.e .— 

4 X 0"033 = O’ 13 ohms. 

The required external resistance is therefore— 

1-066 — 0-13 = 0-934 ohms. 

With increasing speed, the decrease in the tractive force and in the rate of 
acceleration, was derived in the previous case. The rate of decrease with increasing 
speed is now, however, considerably greater, as the total counter-E.M.F. (i.e., the 
counter-E.M.F. of two motors in series) is, for a given current per motor and a given 

69 













ELECTRIC RAILWAY ENGINEERING 



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speed, exactly double its 
former value. In fact, 
the rate of decrease with 
increasing speed is exactly 
double its former value. 
Thus if, for the parallel 
connection, the current 
reaches a certain mini¬ 
mum value in 2 seconds, 
it will, if the same acce¬ 
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in both cases, reach the 
same minimum value in 
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connection. We can 
therefore at once use the 
curves of Fig. 64 for the 
“ series ” connection by 
simply designating the 
abscissae as 0, 1, 2, 8, etc., 
in place of their original 
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provided that the total 
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0T4, 0"064, 0, as set 
forth in Table XVII. (on 
p. 65). 

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tions, Fig. 64 is at once 
applicable to “ series- 
parallel ” control. In a 
similar way, Figs. 65 and 
66 may be used again, if 
the abscissae and ordinates 
are numbered with half 
their original values. 

After 6-7 ( = ^ ) 

seconds, the last section 
of resistance is cut out, 


70 



































































































































































































































































































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ELECTRIC RAILWAY ENGINEERING 



72 


Time m 'Seconds 

Fig. 76. Series Parallel Operation of Four G.E. 66 A Motors. 

































































































































































































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Speed in f Y l7/es per Hour 

Fiff . 77. Characteristic Curves of Series-Parallel Operation of Pour G.E. 66 A. Motors, with a Gear Ratio of 3-94, and with 34-inch Driving Wheels. 125-ton Train. Level Track. 


30 






































































































































































































































































































































































Pigs. 78 to 80 and Pig. 84 relate to method of series-parallel control corresponding to Method B "I I able XX 





Curves of Total Rheostatic Losses as a Function of Time. 


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Characteristic Corves with Series Parallel Control. 





































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































I 


CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 


and the “ series ” motor curve is reached. This is one of the two most favourable 
points of operation, for all the rheostats are cut out, and no external losses occur. 

Suppose we remain on this point long enough to let the acceleration again drop 
to the minimum value reached on the preceding point, and that we then switch over 
to “ parallel" connection, the current per motor will again vary between the same 
limits as for the full “ parallel ” control, i.e., between 230 amperes and 171 amperes 
per motor. Figs. 64, 65, and 66, are now taken in their original sense, and we start 


again at the ordinate for which the abscissa is equal to 7‘4 


14-8 

2 


) 


seconds. 


In 


Fig. 76, the whole period up to the “ parallel ” motor curve has been plotted. Though 
in both sections the current per motor varies within the same limits, the total current 
input to all motors will in the first section be exactly half of that in the second section. 
Up to this point we have taken a variation of the current per motor between fixed 
maximum and minimum values as the basis on which to build our conclusions. It is 
clear from Fig. 76 that, in the case of “ series-parallel ” control, this basis is no longer 
suitable, since the steps in the total current input would be undesirably large for the 
“ parallel ” section, and needlessly small for the “ series ” section. Moreover, it is 
distinctly preferable to increase the mean rate of acceleration in the “ series ” section, 
and to decrease it in the “ parallel ” section, in order to decrease the maximum current 
taken from the station, which, in the case of Fig. 76, is, for the “parallel” section, 
twice as great as for the “ series ” section. 

Fig. 76 should also be altered so as to increase the time during which the train 
runs on the first “ motor curve,” as this is no less favourable than the second 
“ motor curve.” 

Fig. 61, on p. 65, was used as a means for deriving the speed-time curve with all 
four motors in parallel. For the more general case of “ series-parallel ” control, the 
similar curve sheet shown in Fig. 77 has been prepared. Curves of this sort should 
be prepared for every design of motor, and consulted in all such cases, as they contain 
the solutions to various problems connected with the starting of the train. The speeds 
in miles per hour are plotted as abscissa, and the tractive force in pounds per ton as 
ordinates. Four curves are plotted, namely— 

I. “ Parallel ” motor curve without external resistance; 

II. “ Parallel ” motor curve with 0’5 ohm external resistance ; 

III. “ Series ” motor curve without external resistance ; 

IV. “Series ” motor curve with 1*0 ohm external resistance. 

These curves are the more useful since the curves for any other external 
resistances lie proportionately between I. and II., or between III. and IY. 

Suppose that we have five steps in the “ series ” section of the controller, and 
that the resistance decrease between each step is 0*2 ohms, we can draw in the 
corresponding curves by simply dividing the horizontal distances between I. and III. 
into five equal parts. 

This has been done in deriving the curves shown in Figs. 78, 79 and 80. The 
time for each step is taken approximately constant at P3 seconds, and we see that the 
maximum current per step increases slightly for each succeeding step, while the 
minimum current per step decreases slightly. After switching over to “ parallel,” the 
external resistance is 0’25 ohms, and is switched out in steps of 0’05 ohms. The 
identical rheostat sections employed for the first part, could also be used for the second 
part by having two rows of resistances successively in series and in parallel. The 
curves of Figs. 78, 79, and 80 give acceleration, current, and speed plotted against time. 


73 



ELECTRIC RAILWAY ENGINEERING 


As already pointed out, it is distinctly preferable to increase the rate of accelera¬ 
tion during the “ series ” period, and to decrease it during the “ parallel ” period, in 
order to diminish the maximum current to be supplied by the generating station, 
as well as in order to relieve the motors, especially as regards commutation, of their 
severest work. A case in which this plan has been employed has been worked out in 
Figs. 81, 82, and 83. The total external resistance at starting is 0'9 ohms, and is 
cut out in approximately equal time intervals and in equal resistance sections, until 
the point of operation on the “ series ” motor curve is reached. The motors are 
permitted to run on this point for a considerably longer time than in the case of 
Figs. 78 to 80. The resistances employed during “ parallel” running are again one- 
quarter of those used during operation in “ series,” and are also cut out in equal 
time intervals and in equal steps. It will be seen that the acceleration during the 
period of operation with the “series” connection, is about 30 per cent, larger than 
during operation in “parallel.” Figs. 81,82, and 83 again give acceleration, amperes, 
and speed as a function of the time in seconds. In Figs. 84 and 85 the rheostatic 
losses for these two methods are plotted as a function of the time. The curves of 
Figs. 86 and 87, in which speeds are plotted as abscissae, correspond respectively to 
the groups of curves of Figs. 78 to 80 and Figs. 81 to 83. Before we compare the 
two typical methods of Figs. 86 and 87 (methods B and C of Table XX.), let us 
attempt to simplify the calculations by assuming an infinite number of steps. Fig. 88 
is the equivalent of Fig. 86, and Fig. 89 the equivalent of Fig. 87, the only alteration 
being the assumption of an infinite number of resistance steps. 

Table XX. gives a comparison between the five methods:— 

(A) parallel control ; 


(B) series-parallel control, 1 ohm resistance, ten steps; 

(C) series-parallel control, O'9 ohms resistance, ten steps; 

(D) series-parallel control, corresponding to B, but with an infinite number of steps; 

(E) series-parallel control, corresponding to C, but with an infinite number of steps. 

The method of calculating with the assumption of an infinite number of steps 

(methods D and E of Table XX.) leads to results in nearly all respects equivalent to 
those obtained by the assumption of a few steps, the principal exception being that the 
results for the efficiency are slightly—some 3 per cent.—too high. The table shows 
clearly the advantage of method C as compared with method B. Still more marked is 
the difference between series-parallel control and parallel control. The case of an 
infinite number of steps is not an abstract one, but can be realised by liquid starting 
resistances, as has been done, for instance, on the Valtellina Railway. 

A ith parallel control by method A, the train, in 13'5 seconds, covers a distance of 
138 ft., attains a speed of 13*5 miles per hour, and absorbs 1*51 kilowatt-hours. With 
seiies-parallel control by method C, the train, in 14'0 seconds, covers a distance of 
143 ft., attains a speed of 13'7 miles per hour, and absorbs 1'09 kilowatt-hours. 
A itli seiies-parallel control by method C, the train, in 15'7 seconds, covers a distance 
of 174 ft., attains a speed of 14'2 miles per hour, and absorbs 1*085 kilowatt-hours. 
The maximum load on the generating plant in these three cases is 464, 431, and 396 
kilowatts respectively. The difference between the first two values (464 and 431), cor- 
lesponding respectively to methods A and B, is, however, due entirely to the fact that 
smallei resistance steps are used in the second case than in the first. Between the 
second and third methods (methods B and C) there is, however, a further decrease of 

8 pei cent, in the maximum output required from the generating plant per ton weight 
of train. 


74 


CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 

Table XX. 

Comparison of Five Alternative Methods of Motor Control. 





- £ 

^ 05 

t-. 





-S b 

u 

o H 

0^3 

8- p 




'O 

P <p 

C 2 

CCQ P 

goil 




PQ(S | 

oo J 

OO G 2 ■ 

_ _, -*-> ^ ^ 




50 

a, —; 

2 

Gm m © 

o ® 'Ss b 

£-h a- » 
ei -*ff 

1) 8H73 

p, tc 

O ® tC" a: 
r- ZZ r* P 

813 Cl- 

g S3 CM 0 

O ^ tuo p aj 

iff d p 

S g,g e °> 





c r. P 

a> .e 

Ci EC W 

4J H 

cc ci 

.2 8- 




a; G 

0 

E 





OQ 

b 

SB"? 


t>i , I Dunne; senes control . 

Kheostatic -r> • n i , 

, • i -i Dunne; parallel control 

losses in kilo- f m 4 . i j • • . 

,, t lotal during resistance- 

watt-seconds , n 1 

' control period . 

2,640 

2,640 

616 

560 

1,176 

580 

397 

977 

610 

555 

1,165 

571 

395 

966 

Motor losses 

... * 

480 

449 

467 

455 

480 

Total losses (rheostatic and motor) kilowatt- 






seconds 

...... 

3,120 

1,625 

1,444 

1,620 

1,446 

Acceleration in 

During series control . 

— 

1-0 

1T7 

1-05 

1-18 

miles per hour 

• During parallel control 

10 

0-97 

0-87 

0-97 

0-87 

per second 

Mean on series motor curve 

— 

1-0 

0-75 

0-89 

0-72 

During series control . 

— 

31 

25 

34 

28 

Distance covered 
in feet 

During series motor curve . 
During parallel control 

Up to time of parallel motor 

138 

13-6 

98-7 

51-4 

98 

9-0 

106 

48 

111 


curve .... 

138 

143 

174 

149 

177 


During series control . 

— 

6-4 

5-4 

6-6 

5-7 

Time in seconds - 

During series motor curve . 

— 

1-4 

4-6 

0-8 

4-15 

1 

During parallel control 

At time when series motor 

13-5 

6-2 

5-7 

6-6 

6-3 

1 

curve commences . 

— 

6-5 

6-3 

7-0 

6-7 

Speed attained in j 

Up to end of series motor 






miles per hour 1 

curve .... 

— 

7-75 

9-25 

7-75 

9-3 

Up to time when parallel 







motor curve commences . 

13-5 

13-7 

14-2 

14-2 

14-7 

Maximum input in 
Energy consumed 

kilowatts .... 

) 

464 

431 

396 

390 

360 

by train up to the 

[ Kilowatt-seconds. 

5,440 

3,920 

3,910 

4,180 

4,135 

parallel motor 

[ Kilowatt-hours 

1-51 

1-09 

1-085 

1-16 

115 

curve 







Energy output from axles, in kilowatt-seconds, 






up to parallel motor curve .... 

2,320 

2,295 

2,466 

2,560 

2,689 

Efficiency of system during period of acceleration 
Time in seconds taken during accelerating period 

42% 

58% 

63% 

61% 

65% 

up to parallel motor curve .... 

Mean acceleration from start up to time of com- 

13-5 

14-0 

15-7 

14-0 

161 

mencement of operation on parallel motor curve 

1-0 

0-98 

0-90 

DO 

•91 


These considerations all refer to the accelerating period only. It is clear, how¬ 
ever, that after the time of completion of rheostatic acceleration, there can be no dif¬ 
ference between these various methods. The only effect of also taking this latter period 
into consideration would be to diminish the striking difference existing between these 
methods when the results are reduced to the basis of energy consumption per ton-mile. 

The advantages which we gain by employing, as in method C, a higher rate of 
acceleration during series control than during parallel control, and by running for a 
length of time on the series motor* curve, are— 

(1) Increase of efficiency and 

(2) Decrease of stress on generating station, motors, rolling stock, and per¬ 
manent way. 


75 




























ELECTRIC RAILWAY ENGINEERING 


A close study shows that the first advantage can be directly attributed to the 
longer time at which the train travels on the series motor curve, and the second 
advantage is due entirely to the lower rate of acceleration during the period of running 
with the parallel connection. One might make use of the principles underlying 
method C, to a still greater degree than was done in the case just discussed. For 
instance, Storer advocates (“ Transactions of the American Institution of Electrical 
Engineers” (1908), Vol. XXIV.) that the total current input to the train during series 
control should be as great as during parallel control. The authors are, however, of 
the opinion that such an extreme case introduces grave disadvantages. As the current 
for the normal starting method is already relatively very high, a 60 to 70 per cent, 
increase in the current would tend to undue deterioration of the commutator due to the 
high density at the brush surface area. This would more than offset the gain through 
reducing the normal current during parallel control. The greater acceleration at the 
instant of starting, would also be limited in cases of insufficient weight per axle 
available for adhesion. In the following study we shall neglect altogether any 
advantage that may be gained by thus improving the efficiency during the accelerating 
period, and shall simply use the normal accelerating method for an infinite number 
of controller steps. The simplification thus introduced will facilitate a close 
examination into the period following the completion of rheostatic acceleration. 

In a former chapter, the speed-time curve has been developed graphically, and 
the elementary principles of coasting and braking have been explained, always on the 
assumption of a level track. A shorter, though somewhat less accurate, method, based 
on tabular calculations, will now be given, and the following important relations will 
be considered :— 

(1) Influence of coasting or “ drifting ” ; 

(2) Influence of gradients. 

On a straight level section of 4-mile length, a 120-ton train, equipped with 
four G.E. 66 A motors, the characteristic curves of which have been given in Fig. 50 
(on p. 56), is accelerated at the rate of 1 mile per hour per second. We shall first 
assume that no coasting takes place. 

The speed intervals into which the calculation has been divided, are set forth in 
column 1 of Table XXI. After the completion of rheostatic acceleration, that is, at a 
speed of 14-1 miles per hour, for which the rate of acceleration on the “parallel” 
motor curve is 1*0 mile per hour per second, the speed limits in column 1 are raised 
by increments of 1 mile per hour. Column 2 gives the tractive force exerted by 
the four motors at the average speed during each interval, the values being obtained 
by reference to Fig. 77, as already explained. Column 3 gives the train resistance, 
for which, in lieu of more accurate information, values corresponding with observations 
on the Central London Railway (see Fig. 6, on p. 9) have been employed. The values 
in column 4 are the sum of the values in columns 2 and 3, while column 5 gives 
at once the rate of acceleration in miles per hour per second by simply dividing by 
100 the values in column 4. The values in column 6 are obtained by dividing 
the speed intervals in column 1 by the average accelerations during these intervals. 
The values in column 7 are obtained by multiplying the average speed by the time 
and by the constant 1*47. 


76 


Prolonged interval of operation on Motor Curve prior to going into parallel. No time spent on Motor Curve prior to going into parallel 



Screed m tallies per Hour 

Fig. 86. 

(Method B of Table XX.) 



Fig. 87. 

(Method C of Table XX.) 


2D Curves for the Case of :— 


Infinite Number of Controller Positions. 



Fig. 88. 

(Method D of Table XX.) 



Fig. 89. 

(Method E of Table XX.) 

























































































































































































































































































































































































































































































































































































































































































































































































































































































































ns.ii -■■—■rri i ... . . - ■ . —- _ ___ 

























































































































































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 


Table XXI. 

Calculations for a b-mile run at an Average Speed of 19 miles per hour. 120 -Ton 

Train. Level Track. 


Column 1, 
Speed Intervals. 
(The Speed is 
expressed in Miles 
per Hour.) 

Column 2, 
Tractive Force 
exerted l>y 
Motors in Pounds 
per Ton. 

Column 3, 
Tractive Resist¬ 
ance in Pounds 
per Ton. 

Column 4, 
Resultant 
Accelerating 
Force in Pounds 
per Ton. 

Column 5, 
Rate of Accelera¬ 
tion in Miles per 
Hour per Second. 

Column 6, 
Time in Seconds. 

Column 7, 
Distance in Feet. 

0-14-1 

106 

-6 

100 

10 

14-1 

147 

14-1-15 

96 

— 65 

89-5 

0-895 

10 

21 

15-16 

78 

— 6'5 

71-5 

0-715 

1-4 

33 

16-17 

63 

-7 

56 

0-56 

1-8 

45 

17-18 

52 

-7 

45 

0-45 

2-2 

57 

18-19 

44 

-7 

37 

0-37 

2-7 

72 

19-20 

38 

— 7*5 

30-5 

0-305 

3-3 

96 

20-21 

34 

-7-5 

26-5 

0-265 

3-8 

114 

21-22 

29 

— 8 

21 

0-21 

4-7 

147 

22—23 

26 

-8 

18 

0-18 

5-5 

183 

23-24 

23 

-8 

15 

015 

6-7 

234 

24-25 

20 

-8-5 

11-5 

0115 

8-7 

312 

25-26 

18 

-8-5 

9-5 

0-095 

10-5 

390 

26-26-9 

16-5 

-9 

7-5 

0-075 

11-5 

450 

26-9-0 

-150 

-7 

-157 

-1-57 

171 

95-0 

340 

2,640 


Average speed from start to stop = 19 miles per hour. 
Total watt-hours energy input to train = 4,370. 

Energy input to train in watt-hours per ton-mile = 72-7. 


From these figures we obtain the speed time curve plotted in Fig. 90, in which the 
current input during this period has also been plotted. We have 72‘7 watt-hours per 


3 



Fig. 90. Characteristic Curves for a ^-mile Run at an Average Speed of 19 Miles per 

Hour. 120-Ton Train. Level Track. No Coasting. 

ton mile and an average speed of 19 miles per hour. The curves of Figs. 91, 92, and 93 
have been obtained by similar calculations. In these cases, however, coasting for 

77 




























































































































ELECTRIC RAILWAY ENGINEERING 


various lengths of time has been employed. The results have been brought together 
in Table XXII. It will be seen that the watts input per ton-mile decrease at a 


4 



Pig. 91. Characteristic Curves for a 4-mile Run at an Average Speed of 18-1 Miles 
per Hour. 120-Ton Train. Level Track. Coasting for 39 Seconds. 

considerably greater rate than the average speed. The value 28 '5 watt-hours per 
ton-mile for an average speed of 18*4 miles per hour, and two stops per mile, may be 


$ 

f 

€ 


1 

1 



Pig. 92. Characteristic Curves for a 4-mile Run at an Average Speed of 16*1 Miles 
per Hour. 120-Ton Train. Level Track. Coasting for 72 Seconds. 

considered very small indeed. It would, however, be quite impracticable to employ 
such a large amount of coasting, and this is due to the high momentary maximum 
loads that would be thereby incurred. 


73 


















































































































































































































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 

Table XXII. 

Comparison of Results of mile Runs with various Periods of Coasting. 
Acceleration = 1 mile per hour per second in all cases. • 120 -Ton Train. Level Traci:. 


Number of Seconds 
from Start to 
Commencement 
of Coasting. 

Distance in Feet 
from Start to 
Commencement 
of Coasting. 

Average Speed 
from Start to 
Stop in Miles 
per Hour. 

Energy Input 
to Train in 
Watt-hours per 
Ton-mile. 

Average Kilo¬ 
watt Input 
to Train. 

Maximum Kilo¬ 
watt Input to 
Train. 

Ratio of 
Maximum to 
Average Input. 

No coasting 

No coasting 

18-95 

72-7 

166 

400 

2-4 

47-2 

1.149 

18-10 

52-0 

113 

400 

3-5 

303 

585 

16-05 

38-3 

74 

400 

5-4 

20-5 

303 

13-38 

28-5 

46 

400 

8-7 


By increasing the rate of acceleration at starting, the same average speed may he 
obtained for various intervals of coasting. This has been done in the curves of Figs. 



Fig. 93. Characteristic Curves for a 4-mile Run at an Average Speed of 13-4 Miles 
per Hour. 120-Ton Train. Level Track. Coasting for 107 Seconds. 

94 and 95 for a mean speed of 19 miles per hour, and the results, together with those 
corresponding to Fig. 90, are given in Table XXIII. 


Table XXIII. 


Comparison of Results of Y mile Runs at an Average Speed of 19 Miles per hour, and 
with various Periods of Coasting. 120 -Ton Train. Level Track. Varying rates 
of Acceleration. 


Rate of 

Acceleration in 
Miles per Hour 
per Second. 

Number of 
Seconds from 
Start to Com¬ 
mencement of 
Coasting. 

Distance in 
Feet from Start 
to Commence¬ 
ment of 
Coasting. 

Average Speed 
in Miles 
per Hour. 

Energy Input 
to Train in 
Watt-hours 
per Ton-mile. 

Average 
Kilowatt 
Input to 
Train. 

Maximum 
Kilowatt 
Input to 
Train. 

Ratio Maxi¬ 
mum Input 
to Average 
Input. 

10 

No coasting 

No coasting 

19 

72-8 

166 

400 

2-4 

1-2 

57-5 

1,548 

19 

60-8 

139 

460 

3-3 

1-4 

49-3 

1,344 

19 

56.0 

127 

520 

4-1 


79 












































































































































































ELECTRIC RAILWAY ENGINEERING 


In this comparison the same motor curve has been taken for all cases. A similar 
comparison might be made in which different motor curves are used, the mean speed 
and rate of acceleration remaining the same. Our principal purpose is, however, to 
show that for higher accelerating rates, the watt-hours per ton-mile are slightly 
reduced. Carter, in a letter to Engineering for June 2nd, 1905, writes :— 

“ Paradoxical as it may appear, if a given schedule is to be maintained, the 
higher the rate of acceleration the lower will be the energy consumption per ton-mile. 
The reason, however, is not far to seek. The energy input is employed partly in 
doing work against train resistance, and partly in imparting kinetic energy to the train, 
which is ultimately dissipated through braking. The former component amounts to 
2 watt-hours per ton-mile output for every pound per ton train resistance, say 2^ watt- 
hours per ton-mile output. The latter component, which, in the case of suburban 
service, may amount to two-thirds or more of the total energy consumption, varies 
practically as the square of the speed when the brakes are applied, as the weight of the 
train, and as the frequency of the stops. A higher rate of acceleration therefore results 
in reduced energy consumption, since it becomes possible to maintain the schedule 
with a lower maximum speed, therefore dissipating less energy in braking.” 

The authors wish at this point to refer to the ratio between maximum input to train 
and average input to train. This consideration has a most important bearing on the 
choice of the rate of acceleration to be employed. In the three cases given in Table 
XXIII. (on p. 79) the maximum input to train is respectively 400, 460, and 520, wTiile 
the average input is 166, 138, and 127. The ratio between maximum to average input 
has therefore the values 2*41, 3‘32, and 4'1 for an acceleration of 1, 1*2, and 1‘4 miles 
per hour per second. 

In all those cases where the number of trains running at the same time are few, 
the above ratio plays an important role in so far as the rated output of the generating 
station and of the sub-stations is determined by the maximum output. In all these 
cases it would be bad policy to use a high accelerating rate, as this is associated with 
a high ratio of maximum input to average input. For all those cases, however, where 
the number of trains is great, the value of the maximum input to a single train does 
not occasion great fluctuation in the demand on the generating station, and, therefore, 
a higher rate of acceleration is desirable. Of course, there is still the disadvantage that 
the motors, rolling stock, and permanent w r ay are subjected to more severe maximum 
stresses. 

A e shall now explain a method by which the gradients may be taken into 
account. The method enables us to ascertain the extent to which they influence the 
energy consumption. The influence of a down gradient is added to the tractive force 
exerted by the motor, and that of an up gradient is in opposition to it. As a down 
gradient of 100 per cent., i.e., a direct fall, produces a rate of acceleration of 22 miles 
per hour per second, or a tractive force of 2,200 lbs. per ton, a gradient of 1 per cent, 
will produce a tractive force of 22 lbs. per ton. It is, therefore, quite permissible to 
forthwith ascribe to the gradients the tractive force in pounds per ton corresponding 
to the acceleration which they produce. Thus a 1 per cent, up grade, for example, is 
equivalent to a tractive force of —22 lbs. per ton, and a ^ per cent, down grade 
to +11 lbs. per ton. 

A e shall again consider a +mile section, the first 300 ft. of which have a 
gradient of +60 lbs. per ton, and the last 300 ft. a gradient of — 60 lbs. per ton. The 
remainder of the distance is level. The calculation may be carried out tabularly, as 
set forth in Table XXIV. The results have been plotted in Fig. 96. 

8o 














































































































































































































































so -o 















































































































































' 











































. 























































































Fig. 96. 


Ch ar acteristic Curves for a Half-Mile Eun at an Average Speed 01- 

in Tarle XXIV. 


19 Miles per Hour. 


120-Ton Train. Grades as set forth 








































































































































































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 

Table XXIV. 


Calculations for Operation of a 120 -Ton Train at an average Speed of 19 Miles per Hour, 
over a Mile Section, with a 2’78 per Cent. Down: Gradient for the first 300 Feet, and 
a 2*73 per cent. Up Gradien t for the last 300 Feet. 


Speed. 

Tractive Force 
exerted by 
Motors in Pounds 
per Ton. 

Tractive Force 
exerted by 
Gradient in 
Pounds per Ton. 

Train Resistance 
in Pounds 
per Ton. 

Resultant 
Acceleration in 
Miles per Hour 
per Second. 

Time in 
Seconds. 

Distance in 
Feet. 

0-14-1 

• 

106 

+60 

-6 

1-6 

8-8 

91 

14-1-15 

96 

+ 60 

—6-5 

1-485 

•6 

12 

15-16 

78 

+60 

— 6 - 5 

1-315 

•8 

18 

16-17 

63 

+60 

—7 

1-16 

•9 

21 

17-18 

52 

+60 

—7 

1-05 

•9 

24 

18-19 

44 

+60 

—7 

0-97 

1-0 

27 

19-20 

38 

+60 

—7-5 

0-905 

1-1 

30 

20-21 

34 

+60 

—7-5 

0-865 

1-2 

36 

21-22 

29 

+60 

—8 

0-81 

1-2 

39 

22-28 

26 

0 

—8 

0-18 

5-5 

182 

23-24 

23 

0 

-8 

0-15 

6-7 

231 

24-23 

0 

0 

—8 

—0-08 

12-5 

432 

23-22 

0 

0 

— 8 

—0-08 

12-5 

414 

22-21 

0 

0 

—8 

—0-08 

12-5 

396 

21-20 

0 

0 

—8 

—0-08 

12-5 

387 

20-13-3 

0 

—60 

—7-5 

-—0'675 

9-8 

240 

13-3-0 

—150 

—60 

—6 

—2-16 

6-2 

60 






94-7 

2,640 


Mean speed from start to stop = 19-0 miles per hour. 
Input to train in watt-hours per ton-mile = 30 - 7. 


This value of 39• 7 watt-hours input to the train per ton-mile should be compared 
with the values in Table XXIII. The comparison shows that by a suitable use of this 
method, great economies are possible in many cases. To obtain the full saving possible, 
the use of the brakes should be reduced to a minimum. This condition is often not 
complied with on such roads. One often observes that the motorman keeps on power 
part way up the grade approaching the arrival platform, and then cuts off the current 
and applies the brakes. When such methods are permitted, a large part of the possible 
saving is sacrificed. The percentage of possible saving by the use of gradients at the 
stations, is greater the greater the number of stops, and the higher the schedule speed. 
It would not be worth while providing gradients for this purpose on lines with 
infrequent stops. These gradients are considerably more effective than any schemes 
for regenerating, for the reason that with gradients the recovery of the energy 
represented by the momentum of the train is effected without the aid of the motor, 
i.e., without heating the motor, and it follows directly that the size of the motor can 
be considerably smaller than in any regenerative control system. 

Having shown how to obtain the characteristics relating to each section of a 
railway and how to deduce the average power required corresponding to the average 
speed, the average distance between stops, the profile of the line, and the number of 
trains, we propose to refer briefly to what is known as the load characteristic. It is 
often necessary to ascertain not only the average load but the nature and extent of the 
fluctuations, for the proper proportioning of the generating station plant and sub¬ 
station plant. These are obtained by superimposing the several section characteristics, 
and then adding the ordinates, the intervals corresponding to the frequency of service. 

E.R.E. 8 1 G 









































ELECTRIC RAILWAY ENGINEERING 


In this way the load characteristic is obtained for a particular number of trains. It 
is usual to construct the curve for the maximum number of trains, and, after allowing 
for losses in transmission and transformation, we obtain the conditions to be fulfilled 
by the generating plant. 

We must next consider the choice of the motor and of the gear ratio. The size 
of the motor, so far as relates to its rated output, is mainly dependent upon the 
heating due to the internal losses. The actual size of the motor, however, i.e., its 
weight, is also dependent upon the speed, i.e., upon the gear ratio and upon the 
diameter of the driving wheels. Increasing the gear ratio in any particular motor, 
decreases the train speed and increases the tractive effort both in the same ratio, the 
current being assumed constant. 

In Fig. 97 are given the characteristic curves of the G.E. 66 A. motor for three 
different gear ratios. 1 Curves corresponding to those in Fig. 77 can be plotted for 
other gear ratios in this same way. Fig. 98 shows how the transformation is 
obtained for a 20 per cent, greater gear ratio than that corresponding to the curves in 
Fig. 77. Any alteration in the diameter of the wheels should be treated as equivalent 
to an alteration in the gear ratio, an increase in the wheel diameter being equivalent 
to a decrease of the gear ratio. For instance, if we go over from a gear ratio of 
5’1 to 1 and a wheel of 83 ins. diameter to a gear ratio of 2*7 to 1 and a wheel of 
45 ins. diameter, the equivalent alteration is 


5-1 x 45 
2-7 X 33 


2-58. 


For a given current, the train speed increases in the ratio of 1 to 2*58, and the 
torque decreases in the ratio of 2’58 to 1. 

The method of estimating the temperature rise of a motor must be selected 
with reference to the particular case in hand. In the present discussion we shall 
have occasion to refer more particularly to those cases where the time interval 
from start to stop is small, so small that the temperature rise during one such interval 
can he neglected compared with the total temperature rise of the motor after several 
trips. In such a case we may calculate the copper and iron losses during one run (as 
has been done in Figs. 79 and 82), and thus obtain the average loss, which we 
express in watts. The temperature rise is then obtained from the results of tests made 
with such constant loads as correspond to this value for the average watts dissipated 
in the motor. For preliminary calculations it is usual to estimate the size of the 
motor from the average load of the motors. This may introduce slight errors, since 
the losses during this average load will generally be different from the average losses, 
hut the error is not very great, and, with a little experience in making allowance for 
this error, this simple method can also be used for the final calculation. In cases 
where the average time from start to stop is greater, and a consideration of the heating 
during a single run from start to stop becomes necessary, one nevertheless first 
calculates the heating as before. In addition one must, in this case, take into 
consideration the variation in the final temperature during a single run from start to 
stop. The temperature fluctuates even after having attained its final mean value, in 
he way indicated in Fig. 99, in which it is seen that a heating period alternates with 
a cooling period. The maximum temperature is therefore greater than the average 
temperature by approximately half the difference between A and B. The distance 

1 The ratios chosen, i.e., 2, 3, and 4, allow a good comparison ; it is scarcely necessary to point 
out that the precise values are not such as should be employed in practice. 

82 








































































































































* 


7~r<acb/ye force in ibs. 


il 



Pig. 98. 


Characteristic Curves of Series Parallel Operation of Pour G.E. 66 A. Motors with a Gear Ratio of 4-73 ; 

125-Ton Train. Level Track. 


and with 34-inch Driving Wheels. 




















































































































































































































































































































































































































































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 


A B can be estimated fairly accurately from the cooling curve determined during the 
complete tests on the motor, as all the necessary factors, such as time of cooling and 
average temperature, are given. The temperature rise of the motor from the 
commencement of service would follow the curve of Fig. 100, from which we see that 
it increases by steps as section after section of the route is traversed. 

The problem that next arises, consists in applying to practical conditions the 
various results deduced in the preceding sections. This general case relates to a 
route with a number of stations located at varying distances apart, the gradients on 
each single section also varying. The schedule speed for a total train trip, the 
approximate w T eight of the train, and the duration of the stops are also generally 
given. Before determining the capacity of the motor and the required motor 
characteristics, we must ascertain the average distance between stations and the 
average profile of the line and estimate from these and the other necessary data 
the consumption in watt-hours per ton-mile. While the calculation of the average 
distance between stations offers no difficulty, the average profile of the line is not so 



Fio- 99. Typical Temperature Curve of an intermittently-loaded Motor. 

© 

readily ascertained. In fact, this step is sometimes neglected altogether in the 
preliminary calculation. 

We propose to give a more detailed description of our method for obtaining the 
average profile of the line, because the importance of this factor is often great. In 
very many cases the accuracy obtained from the study of a single representative 
section is sufficient for the final estimation of the required motor characteristics. If 
the average profile is not taken into account, the final and rather laborious calculation 
may show that the preliminary calculations have led to incorrect conclusions as to the 
motor characteristics required, and all the laborious calculations will then have to be 
repeated. If all single sections have approximately the same profile, then, of course, 
the average profile is immediately available. In the general case, however, it is 
necessary to ascertain the degree of importance of the gradients and of their location. 
Such an analysis, as indicated in Table XXIV. on p. 81, would show that an up gradient 
at the beginning of a run is of the greater disadvantage, and that the effect is diminished 
if the location of the gradient is removed from the beginning nearer to the end of the 
accelerating period, and still further diminished if nearer to the end of the run. In 


















































ELECTRIC RAILWAY ENGINEERING 

fact, at the very end of the run an up gradient becomes advantageous, since it relieves 
the brakes. The effect of any gradient may, therefore, be fairly represented as a 
function of the amount of that gradient and of its location. 

Suppose that we have a line where the distance between stations varies between 
one-third of a mile and one and one-half miles. From a rough consideration of the 
mean speed and the practicable rate of acceleration, we find that the accelerating period 
may extend to a distance of from 200 to 500 ft., and the braking period to from 150 
to 250 ft. In Table XXV., the gradients for the three principal stages of each single 
run between stations are recorded. 

I. The average gradient for the first 300 ft. 

II. „ „ „ second 300 ft. 

III. „ „ „ last 200 ft. 

To each gradient is assigned at once its equivalent value in tractive force in 
lbs. per ton. An up-gradient is indicated as negative (—), and a down-gradient as 
positive (+). 

Table XXV. 


Schedule of Gradients on the various Sections of the Railway. 


Run. 

Average Gradient 
for first 300 Feet. 

Average Gradient 
for second 300 Feet. 

Average Gradient 
for last 200 Feet. 

From station A to station B 

+ 20 

+ 15 

+ 5 

From B to C 

+ 10 

+ 3 

+ 11 

From C to I) 

— 5 

-8 

+ 20 

From D to E 

— 6 

-3 

-15 

From E to F 

+ 30 

+ 10 

-5 

From F to G . 

-20 

+ 10 

-25 

Average A to G 

+ 5 

+ 4-5 

-2 


From this table an average gradient for the first 300 ft., for the second 300 ft., 
and for the last 200 ft., is readily obtained, and the average profile of the average 
run, from start to stop, can be determined at once, the intermediate distance being 
taken as level, as the effect of all intermediate gradients is comparatively small unless 
they are very heavy, in which case an allowance should be made in the final result. 
Of course, with sufficient experience, one may make an excellent determination 
of the average profile itself by unaided judgment, thus avoiding the necessity 
for such calculations as those indicated in Table XXV. Armstrong has given very 
convenient curves for cases of just this sort. His curves give the relation between the 
kilowatts input to the train on the one hand, and the stops per mile and the schedule 
speed of the train on the other. Armstrong’s original curves, which are reproduced 
in Fig. 101, give the average kilowatts at the car for a car weighing 32 metric tons. 
The duration of stops appears to have been taken as 20 seconds. In Fig. 102, the same 
curves have been converted by the writers into terms of the watt-hours per ton-mile. 
This is an expression which does not vary greatly with the weight of the car or train. 

Mr. F. W. Garter has kindly placed at our disposal the curve reproduced in 
Fig. 103. In this curve, Carter employs as ordinates the products of rated horse 
power per ton and J stops per mile, and as abscissas the products of mean running 
speed in miles per hour (exclusive of stops) and \/ stops per mile. By this very 
ingenious way of plotting, Carter has been able, in a single curve, to obtain the 

84 























Fig. 100. Curve showing the Temperature Rise of a Railway Motor when running on a Service with Long Coasts and Frequent Stops. 








































































































































































































































































. 






. - — 












































































































































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 


equivalent of Armstrong’s group of curves. The authors have made a comparison 
between Carter’s curve and Armstrong’s curves, and find that the latter curves can be 
represented with great accuracy by a single curve, in which the abscissae denote 
schedule speed x stops per mile, the ordinates denoting horse power per ton x (stops 
per mile) 2 . We have worked out such a curve in Fig. 104 for a 30-ton train. Whereas 
Carter’s curve (Fig. 103) gives the rated capacity (see p. 55 for definition of rated 
capacity of railway motors), the curve of Fig. 104 relates to input to train. In going 
from a 30-ton car to a 100-ton train, the watt-hours per ton-mile will remain practically 



Fig. 101. The Effect of Frequent Stops in High-Speed Railroading. (A. II. Armstrong, 
Street Railway Journal, Yol. XXIII., p. 70, January 9th, 1901.) 

Speed for above curves = Schedule Speed (i.e., including stops). 

The diagram shows the energy consumption for a 32 (metric) ton car. Duration of stops = 20 seconds. 


unchanged in all cases in which the air friction is small compared with the bearing 
friction, or in which the energy for overcoming the friction is small compared with 
the energy wasted in rheostats and braking. In other words, the lower the speed and 
the greater the number the stops per mile, the smaller will be the difference in the 
value of the watt-hours per ton-mile required for a 30-ton train and the value for a 
100-ton train. 


35 





































































































Average Input to Car /n T/adt A/ours per Ton TT/Ie 


ELECTRIC RAILWAY ENGINEERING 

While it lias been repeatedly shown that at medium and high speeds long trains 
require much less energy per ton than is required for short trains, different investigators 



Fig. 102. Energy Consumption for a 32-Ton Car at various Schedule Speeds. 

Duration of stop = 20 seconds. 


have arrived at widely-diverging values for the relative consumption of long and short 
trains. Aspinall’s curves for the tractive force required at the axle for trains of various 
lengths have already been given in Fig. 2 on p. 6 of Chapter I. Armstrong, basing his 

86 















































































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 




v. 

* 

-<o 

'e 

o; 


conclusions on exhaustive tests by Davis, employs the curves reproduced in Fig. 105, 
in deducing the relative amounts of tractive force required for light and heavy trains. 
It is most difficult to reconcile these and other results, as well as to deduce a practical 
method of allowing for the variations in power required due to variations in the 
weight of the train, but these curves are useful as guides in such cases. 

On p. 248 of The Electric Journal for May, 1906, Wynne has given 
some curves plotted from 

a formula by Blood, and ftzbed Power of Motors for fire rage Sub urban 

showing the train resistance Conditions 

of single cars of different deceleration=/5 fCi/tsper Hour per Second 

weights. These curves have braking =/ /& r ' m ' ' 

been replotted employing Coasting * If5% of Running Time/Ecludinq Stops) 

metric tons, and are given ' ' ' 

in Fig. 106. 

It is convenient for 
any particular case, to 
determine the required 
motor capacity by means 
of curves such as those 
just described, and then to 
increase this capacity by 
an amount commensurate 
with the conditions as to 
permanent way, gradients, 
curvature and rolling stock, 
for the particular case 
under consideration. 

In comparing the 
above data with experi¬ 
mental results obtained on 
different lines, it must be 
kept in mind that an 
absolute agreement is 
quite out of the question. 

The rating of the motors 
actually installed on the 
trains depends also, as has 
been explained, on the 

gradients and curvatures on the line. Even if these factors were eliminated, there 
would still be the individual judgment of the designer to be considered. Never¬ 
theless, it is of interest to give the rated horse-power of the motor equipment 
chosen for a series of lines operated by continuous-current. These have been 
compiled in Table XXYI. from data for a considerable portion of which we are 
indebted to Mr. F. W. Carter. 











1 











/ 











/ 
















































































































2 

0 22 24- 26 2 

3 30 SZ 34 & 53 AO 


(f\re,rageSpeedfrom5tartCo5topin MPfijx,jfkops perPhe) 


Fig. 103. 


Carter’s Curve of rated Capacity of 
Electrical Equipment. 































ELECTRIC RAILWAY ENGINEERING 

Table XXYI. 


Continuous Current Motor Equipments employed on a Number of Typical Railways. 


Name of Line. 

Schedule Speed in 
Miles per Hour 
(including Stops). 

Number of Stops 
per Mile (the Stops 
are generally of 
from 10 to 20 
Seconds’ Duration. 
The Mean Value of 
15 Seconds may be 
taken). 

Weight of Car or 
Train (including 
Equipment) in 
Metric Tons of 
1,000 Kilogrammes 
(2,200 lbs.). 

Rated Horse-power 
of Motors Installed 
on Car or Train, 
per Ton Weight of 
Train. This Rating 
is the Standard 
Nominal Rating of 
75° C. Rise after 
One Hour on 
Testing Stand. 

Metropolitan District Underground 
Railway of London 

15-7 

21 

175 

6-8 

Manhattan Elevated Railway . 

14-7 

30 

127 

7-9 

New York Rapid Transit Railway . 

16-2 

26 

162 

74 

Liverpool Overhead Railway . 

19 

2-5 

55 

7-3 

Central London Railway . 

14 

21 

120 

4-2 

Illinois Central Railway (Single Car) 

17-8 

1-8 

29 

8-7 

North Eastern Railway . 

22 

0-9 

92 

54 

Railway A — Express Service . 

30-7 

0-8 

64 

12-5 

,, Local Service 

19 

2-6 

64 

12-5 

,, Express Service . 

30-7 

0-8 

48 

14-6 

,, Local Service 

191 

2-6 

48 

14-6 


Carter (“ Technical Considerations in Electric Railway Engineering ”) states that 
on the 1-hour 75° Cent, basis of rating of railway motors, the weight of the 
electrical equipment comprising continuous current motors, rheostats and controllers, 
may be taken as 40 lbs. (18’2 kgs.) per nominal horse-power. He states that this is 
an average figure corresponding to surburban service, and must, of course, only he 
treated as a first approximation. The figure is furthermore based on motors of from 
150 horse-power to 175 horse-power rated capacity. The equipment will be heavier 
with many motors, each of smaller capacity, and rice versa. He also points out in this 
connection, the importance of not overlooking the greater weight of motor trucks as 
compared with trailer trucks. On the basis of this figure of 40 lbs. per rated horse¬ 
power, Carter has deduced curves from which the writers have compiled the curves in 
Fig. 107. It is very evident that for each length of run there is a limiting average 
speed from start to stop which, even with high initial accelerating rates, cannot be 
obtained owing to the electrical equipment requiring its entire available capacity for 
self-propulsion, there being no residue for trucks, cabs, furnishings or for the load to be 
transported. This limiting speed is, of course, higher the less the frequency of stops. 

The curves of total energy consumption at the contact shoe, per ton-mile, 
corresponding to the curves in Fig. 107, are given in Fig. 108 in terms of the 
schedule speed, for stops of 0, 10 and 20 seconds’ duration. Allusion has already 
been made to the importance of a careful examination of any particular case, before 
making definite statements as regards schedule speeds for a given frequency of stops. 
Prior to a discussion of the subject of motor power required for given schedules and 
weight of electrical equipment, the matter could not be dealt with so fully as desirable. 
Now, however, we can revert to the subject and analyse it in the light of the more 
complete data set forth in the last section. 

Schedule Speed and Number of Sto})s per Mile. 

One of electricity’s chief claims to superiority over steam as a motive power for 
railways is based upon the feasibility of maintaining a high schedule speed with frequent 

88 














































































































































































































































5 peed in M/Ies per Hour 



Fig. 105. Armstrongs Curves for showing tiie Variations in Train Resistance with Size and Steed of Train. 




























































































































































































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 


stops. The high rate of acceleration obtainable by electric traction permits higher 
speeds, with a given number of stops per mile, than has been possible with steam 
motive power, but these possibilities have so encouraged promoters of electric traction 



Duration of stop = 20 seconds. 


enterprises that they sometimes lose sight of the fact that even electric traction has 
its limitations, and that high schedule speeds, which, with frequent stops, inevitably 

89 






































































































ELECTRIC RAILWAY ENGINEERING 


necessitate high accelerating rates, are only to he attained at very disproportionately 
increased cost. Limitations of space will only permit of the most cursory examination 
of the subject. By steam traction on railways, the rate of acceleration is generally 
considerably lower than 0*5 mile per hour per second, and one is able by electric 
motive power to obtain accelerating rates as high as 3 miles per hour per second ; 
but it should not be concluded that such accelerating rates are desirable. They 
impose severe strains on the trucks and the permanent way; they involve the use of 
a total weight of electrical equipment, including motors, controllers, and regulating 
apparatus—such as rheostats or transformers, or potential regulators—which may 
exceed the weight of the remainder of the rolling stock, together with the passengers. 



5 /o '5 ao es 30 35 40 so 

7~re>cLire /Tes/sfance in founds per 7on 

Fig. 106. Curves oe Tractive Resistance for Single Cars of various Weights 

according TO Wynne. (Blood’s Formula.) 

The passengers might be willing to sacrifice their personal comfort in the interests of 
shortening the time spent on the journey, but difficulty will attend adjusting fares at 
values commensurate with the expenses entailed in conforming to schedules requiring 
so high an accelerating rate. Of course, it must be admitted that conditions of traffic 
exist where the high train load factor justifies the heavy cost per train mile, and there 
is also the off-setting factor that the higher mileage per train per day reduces the 
number of trains required for a given frequency of service, and thus also the capital 
outlay for rolling stock. The greater wear and tear will, however, reduce this 
advantage considerably, in that a larger percentage of the trains will be undergoing 
repairs ; in other words, a larger percentage of spare trains must be provided. 

Leaving out the exceptional cases, it may be said that an average accelerating rate 

90 





























































CHARACTERISTICS OF ELECTRIC RAILWAY MOIORS 

of 1-5 miles per hour per second is generally a fairly satisfactory value for passenger 
trains electrically operated, and is rarely or never exceeded in regular service 11ns 
is already over three times as great as the accelerating rates customary with steam 
passenger trains. The average rate of retardation during braking may also be taken 
at some V5 miles per hour per second. Let us permit the maximum speed to exceed 
the average speed from start to stop by 88* per cent., an average speed 

of 15 miles per hour from start to stop, let us permit a maximum speed of 20 es 
per hour. Let the length of stop equal 15 seconds. With these assumptions, it 
may readily be found by graphical plotting that, with one stop per mile the average 
obtainable speed between stops hardly exceeds 31 miles per hour, or a schedule speed 
(average speed, including stops) of 27 miles per hour. With two stops pei mm 
(».«., one stop every 0*5 mile), the greatest obtainable schedule speed on these same 
assumptions, will be but 19 miles per hour. On the contrary, should ve run 
over sections of 2 miles’ length between stops, we shall lie able to obtain a schec ^ 
speed of 40 miles per hour. These results are brought together in Table XXA . 

Table XXYII. 

Schedule Speed with 15 Second Stops, for a mean Acceleration of 1'5 hides per llonr 
per Second, and a mam Retardation of 1'5 Miles per Hour per Second, when the 
Maximum Speed does not exceed the average Speed from Start to Stop by mot, 
than 33* per Cent 1 


Number of Stops 
per Mile. 

Greatest obtainable Schedule 
Speed. 

2-0 

19 miles per hour. 

1-0 

27 v >> 

0-5 

40 ,, >> 


In a very interesting article on this euhject iowe« ««»"«> Journal, \ol. XXIII 
,,,, 70 71 January 9th, 1904) Armstrong has given data from which the aveiage 
kilowatts input to the train, and the rated horse-power of the e ectnc eqmpmen o 
a 100-ton train, has been obtained for the three cases above considered. 1 
are set forth in Table XXA III. 

Table XXAYII. 

Armstrong's Data for average Input to Tram under various Conditions of Service 

(see Fig. 101). 


Number of Stops 
per Mile. 

Schedule Speed. 

Average Kilowatt 
Input to 
100-Ton Train. 

Rated Horse-power 
of Equipment of 
100-Ton Train. 

2‘0 

19 

140 

630 

1 -0 

27 

230 

1,000 

0-5 

40 

400 

1,800 


‘ W'W’ :L e th"peea 8 ‘in the cX wkh two stops per mile, a schedule speed of 
stops, is termed the 1 i * 29-6 miles per hour, and a maximum speed 

i) axitsast —- - - - 

than the schedule speed. 


91 













92 


Fig. 107, Curves compiled from Carter’s Data on Weights of Continuous-Current Equipments. 






















































































































































































































































































































































































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93 


Fi‘>-. 108. Curves of Total Energy Consumption at the Contact Shoe per Ton-Mile. 






















































































































































































































































































































































































































































































































































































































































ELECTRIC RAILWAY ENGINEERING 


From data of the weight of complete electrical equipments, including continuous- 
current motors and accessories, the rough values set forth in Table XXIX. have been 
compiled:— 

Table XXIX. 

Representative Data of Trains for various Services. 


Number of Stops 
per Mile. 

Schedule Speed. 

Train weighing 100 Tons complete, 
including Equipment and Passengers. 

Seating 

Capacity. 

Weight, Electrical 
Equipment. 

Weight remainder, 
including 
Passengers. 



Tons. 

Tons. 


2-0 

19 

30 

70 

220 

1-0 

27 

40 

60 

180 

0-5 

40 

65 

35 

100 


From the values in Tables XXVIII. and XXIX., the figures shown in Table XXX. 
for the watt hours per seat-mile are readily deduced :— 

Table XXX. 

Watt-hours Input to Trains for various Services per Seat-mile. 


Number of Stops 
per Mile. 

Schedule Speed in 
Miles per Hour. 

Watt-hours Input 
to Train per 
Seat-mile. 

2-0 

19 

34 

10 

27 

48 

0‘5 

40 

100 


Now let us make a rough estimate of the schedule speed which would he 
practicable with two, one, and one-half stops per mile, if we allow 30 tons for 
the electrical equipment, i.e., 30 per cent, of the total weight of the loaded train. 
There thus remains 70 tons for the balance of the equipment, which will provide 
for some 220 seats. Thirty tons of electrical equipment may he taken as corresponding 
to some 630 rated horse-power, and this will provide an average input to train of 
some 140 kilowatts. From Armstrong’s curves in Fig. 101, and from the reasoning 
above employed, the following schedule speeds and energy consumption at train in 
watt-hours per seat-mile may be deduced, and are given in Table XXXI. 

Table XXXI. 

Watt-hours Input to Trains for various Services per Seat-mile. 


Number of Stops 
per Mile. 

Schedule Speed in 
Miles per Hour for 
630 Rated Horse¬ 
power of Electrical 
Equipment. 

Watt-hours Input 
to 100-Ton Train 
per Seat-mile. 

2-0 

19 

34 

1-0 

24 

27 

0'5 

30 

21 


94 

































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 

In Table XXXII. some further conclusions are derived from the preceding tables. 

Table XXXII. 


Dependence of Energy Consumption on Schedule Speed. 


Number 
of Stops 
per 
Mile. 

A. 

Highest practicable 
Schedule Speed (with 
1*5 Miles per Hour 
per Second Accelera¬ 
tion and Retardation, 
also Maximum Speed 
not over 1J x Average 
Speed. 

B. 

Schedule Speed 
corresponding to an 
Electrical Equipment 
constituting 30 per 
cent, of the total 
Weight of Train. 

Percent, by 
which Speed B 
is less than 
Speed A. 

C. 

Watt- 
hours 
per 
Seat- 
mile 
for A. 

D. 

Watt- 
hours 
per 
Seat- 
mile 
for B. 

Percent, by 
which D is 
less than C. 

. Per cent. 
Decrease in 
Energy Con¬ 
sumption per 
Seat-mile, per 
per cent. 
Decrease in 
Schedule Speed. 

2-0 

19 miles per hour. 

19 miles per hour. 

0 per cent. 

84 

34 

0 per cent. 

— 

1-0 

27 ,, ‘ ,, 

24 ,, * „ 

11 

48 

27 

44 ,, 

4'0 per cent. 

0'5 

40 ,, ,, 

30 ,, ,, 

25 

100 

21 

79 

3*2 > > 


It is thus evident that for the first 10 per cent, to 25 per cent, or so, by which we 
reduce the schedule speed below the maximum practically obtainable, we shall 1 educe 
the energy consumption per seat-mile by from 3 per cent, to 4 per cent, for eveiy 1 pei 
cent, decrease in schedule speed; thus we can halve the watt-hours per seat-mile by a 
15 per cent, decrease in the schedule speed below the maximum attainable undei the 
specified conditions. Schedules requiring over 40 watt-hours input pei seat-mile aie 
for trains essentially extravagant. As an example of a much more moderate service, 
the Central London Railway may be mentioned. On this road, the weight of the 
electrical equipment is some 20 per cent, of the total train weight, and the eneig}' 
consumption at the train is of the nature of 20 watt-hours per seat-mile, the a\eiage 
number of stops being 2'25 per mile, and the schedule speed being 14 miles pei houi. 
But in the case of the Central London Railway, the inclines at the station appioaches, 
contribute considerably in decreasing the energy input per train mile. 

The estimations throughout this investigation are of the roughest natuie, and die 
only intended to show the consequences of striving for high schedule speeds and fiequent 
stops. Thus one might very properly question whether a train weighing 100 tons 
complete, and electrically equipped with power for so high schedule and maximum 
speeds as 40 and 53 miles per hour, respectively, with one stop per 2 miles, would or 
would not have the stated capacity of 100 seats. Standards for good piactice in these 
directions are only slowly emerging. In many other respects the estimates aie most 
crude, but it is thought that they may suffice to illustrate the point in question. 

These considerations vitally affect the question of the relative advantages of the 
continuous-current and the single-phase systems. An equipment with alternating 
current single-phase commutator motors and the necessary controlling apparatus for 
running over not only alternating current, but also continuous cunent sections of line, 
may be taken as weighing at least some 40 per cent. 1 more than the conesponding 
equipment of standard continuous-current motors. For a given total weight of tiam, 
this will either necessitate reducing the seating capacity or reducing the schedule 
speed or the number of stops. If the total weight of train is incieased so as to 
obtain the same seating capacit} 7 , then the watt-hours per train-mile will be inciease , 
and this will require for a given schedule a greater rated horse-power per seat. 

Let us confine our comparison to the same total weight of train 100 tons 
already considered. The single-phase equipment will weigh, say L4 x 30 = 42 tons. 

With the remaining 58 tons we can provide seating capacity for some 18‘ 

1 This low figure of 40 per cent, greater weight is only taken from motives of conservatism. 

95 

























ELECTRIC RAILWAY ENGINEERING 


passengers. Neglecting the lower efficiency of the single-phase system, we obtain the 
figures given in Table XXXIII. 

Table XXXIII. 

Comparison of Input per Seat-mile, with Continuous-current and Single-phase Equipments. 


Number of Stops 
per Mile. 

Schedule Speed in 
Miles per Hour for 
630 Rated Horse¬ 
power of Electrical 
Equipment. 

Watt-hours Input to 100-Ton Train 
per Seat-mile. 

Continuous-current 

Equipment. 

Single-phase 

Equipment. 

2-0 

19 

34 

41 

1-0 

24 

27 

33 

0-5 

30 

21 

25 


As a matter of fact, the lower efficiency of the single-phase equipment will make 
these figures still more unfavourable to that system. Should we keep the seating 
capacity the same, we should be obliged to reduce the size of the equipment to not 
over 450 horse-power, and we should then have the schedule speeds and watt-hours 
per ton-mile for the two systems, as shown in Table XXXIV. 


Table XXXIV. 


Further Comparisons of Input with Continuous-current and Single-phase Equipments. 



Schedule Speed in Miles per Hour. 

Watt-hours Input to 100-ton Train per 
Seat mile. 






Number of Stops 
per Mile. 

Continuous-current 
Equipment of 

630 Horse-power, 
and weighing 

30 Tons. 

Single-phase 
Equipment of 

450 Horse-power, 
and weighing 

30 Tons. 

Continuous-current 

Equipment. 

Single-phase 

Equipment. 

2-0 

19 

17 

34 

30 

1-0 

24 

21 

27 

24 

0-5 

30 

26 

21 

18 


By interpolation from the two preceding tables, it is seen that for the same watt- 
hours per seat-mile for the two systems the schedule speeds would be as shown in 
Table XXXV. 

Table XXXV. 


Comparison of Schedule Speeds with Continuous-current and Single-phase Equipments. 


Number of Stops 
per Mile. 

Watt-hours Input 
to 100-Ton Train 
per Seat-mile. 

Schedule Speed in Miles per Hout. 

Continuous-current 

Equipment. 

Single-phase 

Equipment. 

2*0 

34 

19 

18 

1-0 

27 

24 

22 

0-5 

21 

30 

28 


Furthermore, there is as yet no accessible comparative data to make it clear that 
the commutator of the single-phase motor will not deteriorate far more rapidly for a 
mean accelerating rate of 1*5 miles per hour per second than will the commutator of 
the continuous-current motor. Many engineers are quite satisfied that the former will 

96 







































CHARACTERISTICS OF ELECTRIC RAILWAY MOTORS 


deteriorate far more rapidly. It would be well, pending the further development of 
this class of motor, to specify that such motors shall he subjected on the testing stand 
to accelerating on an alternating current circuit from rest up to 20, BO, or 40 miles per 
hour, as the case may be, under such conditions of terminal voltage and load as 
would in actual practice give a constant accelerating rate of somewhat over' 1*5 miles 
per hour per second with the car or train to he handled. If the motor is for a road 
operating with one stop per mile at a schedule speed of 20 miles per hour, this 
acceleration from rest should be repeated every 3 minutes for 15 hours per day for 
10 days. If the commutators of 2 or 3 motors should be shown to sustain this test 
anywhere nearly as satisfactorily as the commutators of corresponding continuous- 
current motors, this commutation menace would be removed from the question, and 
the chief remaining disadvantages of the single-phase equipment would relate to its 
greater weight and lower efficiency. The matter has been alluded to, since attractive 
schedules for suburban trains are dependent upon the use of accelerating rates of 
from 1 to 2 miles per hour per second, and there appears to be room for doubt whether 
the single-phase commutator motor can equal the continuous-current motor with 
respect to good commutation under these conditions. Should this be so, then the 
use of the single-phase system will entail still further decrease in schedule speeds 
below those practicable with continuous-current equipments. Single-phase equipments 
will, of course, permit of much better schedule speeds for suburban service than are 
obtainable with steam locomotives, but it is probable that they will, to many of us, 
prove to be disappointingly inferior to continuous-current equipments. 


r 


E.R.E. 


97 


II 





Part II 

THE GENERATION AND TRANSMISSION OF 
THE ELECTRICAL ENERGY 


H 2 




Chapter V 

THE ELECTRICAL POWER GENERATING PLANT 

T HE amount of power to be provided by the generating station under service 
conditions has been dealt with in a previous chapter. For tramways working 
under normal conditions as to surface characteristics and rolling stock, the average 
power required at the generating station works out at about 7*8 kilowatts per car. 
The maximum fluctuation is from 50 per cent, to 100 per cent, in excess of this, 
according to the number of cars in service and the extent of the undertaking. It has 
been shown that in regard to the generating plant for a railway, a close investigation 
of the conditions of each undertaking is necessary, as the factors vary considerably. It 
has been shown how to take account of these variables, and how to derive, from the 
power curve of each section, a total output curve for the sub-stations and geneiating 
station, from which are obtained the average power, the magnitude, and frequency of the 
fluctuations. The present chapter will deal with the arrangement of the generating 
plant, and the design and characteristics of the component parts. 

Taking as our starting point the load curve of the station, the next step is to 
decide upon the size of unit and the type of generating plant. The daily load curve 
should he consulted to determine the most suitable size of unit, which should lie such 
as to give the highest load factor for the running plant consistent with steam 
economv, operating expenses, and capital cost. The range of load ovei which the 
generating set will maintain a suitable efficiency also enters into the question of its 
size, which should be increased until the extra steam consumption due to the poorer 
load factor balances the saving in capital cost and operating expenses. Under these 
conditions, the size of the generating set will increase with the size of the station up 
to the limit where mechanical unwieldiness interferes with operating economies. A 
limit of 5,000 kilowatts appears to be reached with reciprocating engines, but steam 
turbines appear to have a far higher limit than this, and foi this leason, otliei 
conditions being favourable, it is probable that turbines will be favoured for future 

large installations. . 

Fig. 109 shows a daily load curve of the Central London Railway, and m the same 

diagram is drawn a line indicating the full rated output of the plant in service, the 
ratio of the two areas being the load factor of the plant. In this case six units o 
plant are installed, and the units in service during the particular day vary from one 
to five, and follow the load curve fairly closely. The momentary fluctuations m the load 
are not shown in this curve, and these, of course, have to be taken into account m 
adjusting the plant to the load. It will be seen how the peaks of the load are supplied 
from the overload capacity of the generators. In this connection the curve of tie 
combined efficiency of the engine and generator is of importance, for by designing t le 

IOI 



6C 


102 


109. Central London Railway : Daily Load Curve. 




















































































































































THE ELECTRICAL POWER GENERATING PLANT 


engine and generator with a high level of efficiency over a long range a larger unit of 
plant might he used. This, however, tends to limit the overload margin of the set. 
Superheating of the steam has a tendency to preserve a high level of efficiency over a 
wide range, so that larger units may he used with good economy than otherwise would 
he advisable. 

The amount of spare plant depends upon how often the plant is called upon to 
meet abnormal demands. Tramways, for instance, are liable to heavy loads on one or 
two days in the week, and to a still heavier one on special occasions, such as public 
holidays. To meet the former condition a single unit of plant may be provided as 
spare, while in the case of infrequent maxima it is sufficient to arrange that the whole 
of the plant shall be in service for the occasion, provided that the plant is of a reliable 
type, and the intervals sufficient to attend to repairs. 

With regard to the type of generating plant, provided that the space at one’s 
disposal and the characteristics of the load be taken into account, such matteis as the 
choice of a plant resolve themselves into a question of capital cost against running 
cost. Broadly speaking, for a large installation with large units, a slow-speed engine 
or a steam turbine would be more suitable than a high-speed reciprocating engine. 
The former would be used if the facilities for condensing he limited, and the turbine if 
there is abundance of condensing water at a convenient level not involving much extra 
power in lifting. In the case of a small installation, where the size of units is under 
say 500 kilowatts, the high-speed reciprocating set would be found more suitable than 
a slow-speed set: and if the condensing facilities are limited, a steam turbine is out of 
the question as against a high-speed set, as the latter is not much more expensive, and 
is more economical under the circumstances. 

In order to fulfil the conditions outlined, the engine and generator must be 
designed so as to respond readily to rapid fluctuations in the load. As regards the 
engine, the speed-regulating apparatus must be so designed that the variations of the 
speed from no load to full load, and also during each revolution, must be kept within 
the defined limits. It is usual to specify that the maximum variation in speed due to 
any variation in load between minimum and maximum shall not exceed \\ P er cent - 
above or below the normal speed. 

With regard to the first condition, the difference between the mean speed revolu¬ 
tions per minute at maximum and minimum load is dependent entirely upon the 
governor, but variations during any one revolution must be taken care of by the 
flywheel. These latter variations may be divided into two classes: first, those due 
to variations in the impelling force, the load remaining constant; secondly, those due 
to variations in the load without corresponding increase of the impelling force. 

It has been found in practice for engines for electric traction purposes that the 
weight of flywheel necessary to maintain the speed between the fixed limits is much 
greater for the second than for the first of these conditions, and that if designed to 
fulfil the second, the flywheel will, in a well-balanced engine, be more than sufficient 
to deal with the variations in angular velocity due to variation in the impelling foice. 

The weight of the flywheel rim must be such that the energy given out in dropping 
through the allowable limit of speed variation during one revolution must be equal 
to the increase of load beyond that which can he dealt with by the energy expended 

by the steam available. . , . . . ,, 

It has been found in practice that the maximum energy which the flywheel should 

be designed to supply under these conditions is about 80 per cent, of the maximum 
fluctuation of load to be dealt with. 


103 


ELECTRIC RAILWAY ENGINEERING 


In designing the flywheel the effect of the revolving field or armature of the 
generator should be taken into consideration, and the weight of the wheel reduced 
accordingly. 

As regards the variation of angular velocity during a revolution, the limits depend 
upon the design and type of generator and upon the periodicity. With alternators 
running in parallel, it is found, as a matter of experience, that in order to avoid 
fluctuations of voltage in the system, it is advisable to confine the angular displacement 
to within the limits of 2j electrical degrees above or below the mean. 

The rapid alterations in the stresses and the weight of the flywheel necessitate a 
stiff shaft, but it is found advantageous to make the shaft considerably stiffer than 
these considerations alone would demand, as by this means undue stresses upon the 
reciprocating parts are avoided. These parts can then be designed strictly to fulfil 
their normal functions, and in consequence can be made much lighter than is otherwise 
the case. 

As regards the generator, if of the continuous current type the conditions to he 
fulfilled are met by designing the armature coils for a sufficiently low inductance, a 
high magnetisation of the armature projections, and by over-compounding ; by these 
means sparkless commutation may he obtained throughout a wide range of load. The 
generator is usually required to supply its full rated load continuously without a rise 
of more than 35 degrees Cent., and must, with fixed brush position for all loads, take 
50 per cent, overload without sparking at the commutator. If the generator he of 
the alternating current type, in addition to the considerations mentioned as to varia¬ 
tion in load, consideration must he given to the transmission, transforming, and 
converting system, in fact the whole system is closely interdependent. The design 
of the generator is affected by the resistance and inductance of the transmission 
system and by the nature and electrical properties of the sub-station plant, and the 
properties and characteristics of the whole must be kept in viev r in the design of 
each part. 

The following is a specification of a type of engine and generator which has found 
extensive application in this country; the unit consists of a vertical cross compound 
engine coupled to a continuous current generator of 550 kilowatts rated output, and 
suitable for electric traction purposes. 


Engine :— 

Diameter of high-pressure cylinder ... 22 ins. 

Diameter of low-pressure cylinder . . . 44 ,, 

Stroke . . . . . . . . 42 ,, 

Revolutions per minute ..... 90 

Initial steam pressure ...... 150 lbs. 

Vacuum ........ 26 ins. 

Rated load, (I.H.-P.) 800 ; cut-off, one-third stroke. 

Total weight of engine . . . . . .120 tons. 


Weight of wheel, 70,000 lbs. 
Diameter of bearing, 18 ins. 


diameter, 19 ft. 
length, 86 ins. 


Diameter of shaft between bearings 


face, 16 ins. 

. 19J ins. 


Diameter of crank-pin, 6 ins.; length, 6 ins. 

Diameter of cross-head pin, 6 ins. ; length, 6 ins. 

Diameter of piston rod ...... 4§ ins. 

Diameter of steam inlet, 7 ins. ; diameter of 
exhaust outlet, 16 ins. 

Guaranteed steam consumption .... 13 lbs. of dry saturated steam per 

I.H.P. hour. 


104 





THE ELECTRICAL POWER GENERATING PLANT 


Genera tor :— 


Rated output ...... 

Pressure : no load, 500 volts; full load, 550 volts 
Current........ 

Speed ........ 

Armature winding :— 

Number of circuits ..... 

Number of turns in series per circuit . 

Size of conductor ...... 

Amperes per square inch of conductor . 

Number of slots . . . . . 

Number of conductors per slot 

Diameter of armature at face . . : 

Length of core between heads 

Dimensions of slots ..... 

Field ivinding :— 

Type. 

Number of turns per shunt spool . 

Size of conductor in shunt winding 

Turns per series spool ..... 

Size of conductor ...... 

Commuta tor :— 

Diameter ....... 

Active length ...... 

Number of segments ..... 

Brushes ....... 


550 kilowatts. 

1,000 amperes. 

90 revolutions per minute. 

10 

90 

0'8 ins. x 0‘08 ins. 

1,560 

300 

6 

96 ins. 

20'5 ins. 

2 ins. X 0’525 ins. 

Compound. 

1,154 

f 780 turns of No. 9 B. and S. 

{ 374 ,, No. 10 ,, „ 

8i 

T45 ins. X 6'5 ins. 

86 ins. 

8'875 ins. 

900 

f in. x 1J ins., five per stud, ten 
studs. 


Amperes per square inch of brush contact . . 42 - 8 

Heating :— 

Rise in temperature after eight hours’ run at 
550 volts and 1,000 amperes : — 

Armature core surface ..... 26 degs. Cent. 

Commutator bars . • • • • . 22 ,, ,, 

Spool shunt . . . • • • . 26 ,, ,, 

Insulation Test :— 

2,000 volts effective alternating pressure applied 
for one minute, between the electric circuits 
and framework. 


Efficiency :— 

One and a quarterload 
Full load 

Three-quarter load 
Half-load 
Quarter-load . 
Weight, total . 


94 - 4 per cent. 
94-5 „ 

94-5 
94-0 
91-0 
37 tons. 


In the following specification are given particulars of a vertical 3-cylmder 
compound engine and 2,500-kilowatt three phase generator, also designed foi tiaction 

purposes. 

Engine :— 

Diameter of high-pressure cylinder 
Diameter of low-pressure cylinders 
Stroke ..•••• 

Speed ...... 

Initial steam pressure . 

Vacuum . 


42 ins. 

62 ins. and 62 ins. 

60 ins. 

75 revolutions per minute. 
150 lbs. 

25 ins. 


105 












ELECTRIC RAILWAY ENGINEERING 


Engine — continued. 

Rated load ......... 

Cut-off .......... 

Total weight of engine ....... 

Flywheel: weight, 100 tons diameter 24 ft. X 26J ins. 
face. 

Diameter of bearings first and second from high-pressure 
end, 22 ins. X 36 ins.; third and fourth, 24 ins. X 
36 ins.; fifth and sixth, 32 ins. X 64 ins.; outer 
bearing, 30 ins. X 48 ins. 

Diameter of shaft at flywheel and armature spider 

Diameter of crank-pins: high-pressure, 12 ins. X 12 ins.; 
first low-pressure, 16 ins. X 12 ins. ; second low- 
pressure, 20 ins. X 12 ins. 

Diameter of cross-bead pins ...... 

Diameter of piston rods ...... 

Diameter of steam inlet ...... 

Diameter of exhaust outlets . . . . . 


4,000 I.H.-P. 
One-third stroke. 
700 tons. 


36 ins. 


12 ins. X 12 ins. 

8 ins. 

14 ins. 

24 ins. and 24 ins. 


Generator :— 

Rated output 
Number of phases 
Connections .... 
Periodicity in cycles per second 
Speed in revolutions per minute 
Voltage between terminals . 
Voltage per phase 
Amperes per phase 
Number of poles . 


2.500 kilowatts. 
3 

Y 

25 

75 

6.500 
3,750 
222 
40 


Armature Iron :— 

External diameter of armature laminations . 

Diameter at the bottom of the slots .... 

Internal diameter of armature laminations . 

Gross length of core between flanges .... 

Effective length of armature core ..... 

Number of slots ........ 

Number of slots per pole per phase .... 

Nett weight of armature laminations after deducting 
slots .......... 


220 ins. 
207J ins. 
200 ins. 

22 ins. 

16'6 ins. 
240 
2 

25,000 lbs. 


Armature Copper :— 

Number of conductors per slot (two in parallel) . . 18 

Total number of conductors ...... 4,320 

Turns in series per phase ...... 360 

Apparent cross-section of two conductors in parallel . 0 - 266 sq. ins. 

Mean length of one turn ...... 97 ins. 

Resistanceof armature winding per phase at 60 degs. Cent. 0T4 ohms. 
Weight of armature copper ...... 7,000 lbs. 


Revolving Field :— 

Radial depth of the air gap at the middle of the pole arc 
Pole face diameter ....... 

Total radial length of magnet core, including pole shoe 
Material of magnet core ...... 

Material of yoke ........ 

Polar pitch at air gap ....... 

Length of pole arc ....... 

Weight of magnet cores (including pole shoes) 

Weight of yoke (exclusive of spider) . . . . 

106 


A i' 1 - 
199§ ins. 

10| ins. 
Laminations 
Cast iron. 
15f ins. 

10 ins. 

19,200 lbs. 
23,000 „ 











THE ELECTRICAL POWER GENERATING PLANT 


Magnet Copper :— 


Number of turns per spool ..... 


42-5 

Size of conductor ....... 


1§ ins. X 0 - 17 ins. 

Resistance per spool at 60 degrees Cent. 


0'0073 ohms. 

Mean length of one field turn .... 


64 ins. 

Total weight of copper in fox-ty spools . 


10,000 lbs. 

Full Load Test :— 

Indicated horse-power ...... 


3,630 

Brake horse-power ...... 


3,480 

Electrical horse-power ...... 


3,350 

Steam per I.H.-P. .... 


12-2 lbs. 

Steam per B.H.-P. ...... 


12-7 „ 

Steam per E.H.-P. ...... 


13-2 „ 

Combined efficiency ...... 

Mechanical efficiency, taking generator efficiency 

as 

92 - 3 per cent. 

96 per cent. ....... 

Permanent variation of speed from mean between 

no 

96-2 

load and full load ...... 


1'5 per cent. 

Efficiency of Generator - 

At full load ....... 


96 

At three-quarter load ...... 


95 

At half-load ........ 


93 


The station should if possible be arranged so that each generating set is piped 
direct from one boiler or battery of boilers, thus forming one complete unit. lliis 
enables the piping to be considerably simplified. Each unit can be operated indepen¬ 
dently ; the steam header can be shut off completely, or can be used to enable any 
engine to be supplied from any boiler. This arrangement of steam piping gi\es good 
facilities for testing, and also provides numerous alternatives for working in the event 
of breakdown. The feed piping should be in duplicate, and all piping should have 
large easy bends where possible, and ample provision should be made for expansion. 

^ The boiler plant should be arranged in units, each unit corresponding as nearly 
as possible to the requirements of one generating set. For small stations the 
Lancashire or tubular types of boiler still hold their own, but owing to the limitations 
of size by considerations of transport, they cannot be economically, installed m any 
but the smallest power stations, as such small units in a large station would involve 
extra capital expenditure on buildings and piping, and an increase in the working cost. 

For large installations, boilers of the water tube type are the rule, for the reason 
that they can be built in large units, 30,000 lbs. per hour at a pressure of 150 lbs. per 
square inch being in common use at the present time. By this means the piping can 
be simplified, and the first cost considerably reduced. Examples of this grouping 
and of the piping thereto will be seen on referring to the descriptive portions of this 

C ^The heating surface required for a steam boiler depends upon the initial and 
final temperatures of the furnace gases and the temperature of the feed water. The 
boiler is most efficient when the furnace temperature is as high, and the fana 
temperature of the gases as low, as possible, and the heating surface will transmit 
from three to five British thermal units per hour per square foot per degree difference 
between the mean temperatures of gases and water, varying according to the 

condition, both internal and external, of the tubes. 

The furnace temperature will depend upon the amount of surplus air necessary 

for combustion, which amount varies considerably with different grades of coal; 

107 



ELECTRIC RAILWAY ENGINEERING 


50 per cent, surplus air is usual for furnaces burning 24 lbs. of small coal per square 
foot per hour, and the corresponding furnace temperature under these conditions will 
be about 2,400 degrees F., varying with the thermal value of the fuel burned. 

The necessary draught for this rate of combustion is about f inch of water, which 
may be produced either by a chimney or by artificial means. 

The most satisfactory results are obtained when the velocity of the flue gases is 
between the limits of 12 to 15 feet per second. The amount of gases to be carried 
off being known, the necessary area of the chimney can be calculated from these 
figures. 

The draught produced by a chimney depends upon its height and the temperature 
of the gases, and increases rapidly with this temperature up to about 300 degrees F., 
when the increased volume of the gases begins to counteract the effect of the increased 
draught until at about 500 degrees F. the weight of air delivered to the furnace is a 
maximum, and for a given height of chimney the weight of air delivered will decrease 
as this temperature is exceeded. The decrease, however, is very slight up to 800 
degrees F., and as the requisite quantity of surplus air for combustion is correspondingly 
less as the rate of combustion is increased, the boiler may be forced by allowing the 
gases to escape at a high temperature, thus increasing the difference of temperature 
between the gases and the water, and increasing the rate of evaporation to meet special 
demands, at the expense of extra chimney losses. 

With the steam pressure at 165 lbs. absolute, which is the usual pressure adopted 
in modern installations, it is found impracticable to reduce the temperature of the 
gases leaving the boiler to less than 500 degrees F., and it follows therefore that a 
thermal gain would result from the introduction of a feed heater or economiser, and 
the consequent reduction of the flue temperature from 500 degrees to the necessary 
chimney temperature of 300 degrees. It will be seen, too, that an additional saving 
of heat can be effected by installing forced or induced draught and reducing the 
temperature of the gases still lower by a further increase in the economiser surface, at 
the same time reducing the height of chimney to that necessary to dissipate the 
products of combustion. 

These thermal gains, however, are not always commercial gains, and when the 
cost of economisers, flue space required, and the working cost of scraper gear and fans 
are taken into account, it will often be found better, from a commercial point of view, 
to allow the gases to escape at 500 degrees, especially when the feed-water has already 
been heated by exhaust steam. No definite rule can be laid down as to the advantages 
or otherwise of forced draught and economisers, owing to the widely varying con¬ 
ditions attaching to individual installations, but it may be taken as a general rule 
that economisers and forced draught should be installed only where the price of coal 
is very high and the feed temperature very low. 

The advantages of superheating have been demonstrated and known for a con¬ 
siderable time, but many difficulties were encountered in adapting engines, pipes, and 
valves so as to withstand the high temperature. These difficulties have now been 
overcome so as to admit of superheating up to 150 degrees F. without any elaborate 
precautions, whilst superheating to the extent of 300 degrees F. and over is practised 
successfully with special precautions. This degree of superheat is apparently 
sufficient to ensure dry steam at the release point, and up to this point the saving 
in steam consumption appears to be about 10 per cent, for every 100 degrees of 
superheat, and a nett saving in heat energy of 6 per cent, for every 100 degrees. 
Above 300 degrees F. the law would probably be different, and it is questionable 

108 


THE ELECTRICAL POWER GENERATING PLANT 


whether there would be any great advantage in working at a higher superheat. The 
figure quoted is for compound engines working at full load with cut-off about one-third 
of the stroke; with steam turbines the saving in steam consumption is about 9 per 
cent, for every 100 degrees of superheat. The question as to whether the super¬ 
heater should be separately fired or fired by hot gases from the boiler furnaces 
depends upon the degree to which it is thought desirable to control the superheating. 
When the superheater is made an adjunct of the boiler, the heat of combustion is 
utilised to the utmost, and the means of control are sufficient for all practical 
purposes. With a steady load the superheating is fairly constant. With large boiler 
units, the tendency is to combine the boiler and superheater and to place the super¬ 
heater so that the hot gases are passed through at an early stage in their course 
from the furnaces into the fine. This ensures sufficient and regular superheating, 
whereas if placed in the boiler uptake, the temperature may fall below the temperature 
necessary to impart the required degree of superheat and subject the superheater 
to a deposit of soot. 

The amount of surface required for superheaters varies according to the condition 
of the surface, but 0’75 B.Th.U. per hour may be taken as the average transference 
for 1 square foot per degree difference of temperature between the mean steam 
temperature and the mean temperature of the hot gases. This rate of transference 
is lower than for boiler heating surface, due to the fact that the resistance to heat 
transference between two gases is higher than between gas and liquid. On the whole 
it w T ould seem that the most economical arrangement of plant is to use superheaters 
as part of the boiler construction. 

Considerable difference of opinion exists as to the relative advantages of 
mechanical stokers and hand firing; this is a matter depending a good deal upon 
the personality of the station superintendent. With the same plant one man will 
get better results from hand firing, and another from mechanical stokers. 

Where large boiler units are to be used, mechanical stokers are almost a neces¬ 
sity, owing to the quantity of coal to be handled and the size of the grate. A boiler 
to evaporate 20,000 lbs. of steam per hour at a pressure of 165 lbs. absolute, would 
consume about 1 ton of coal per hour, and would require a grate area of 130 square 
feet to burn the cheaper classes of coal; a stoker would have considerable difficulty in 
reaching the far end of the furnace and in covering the surface evenly, and, moreover, 
the furnace door would need to be open a considerable proportion of the time and 
interfere seriously with the combustion. 

When mechanical stokers are used, they should be selected with great care and 
should be adapted to burn the particular class and grade of coal available. The 
troubles which have been experienced with mechanical stokers have been due to a 
neglect of the limitations of the mechanical stoker in this respect. 

We come now to the general principles affecting the condensing plant. I he 
question of condensing or non-condensing does not arise in tramway or railway work, 
as the benefits to be derived from condensing are only doubtful when a plant is for 
occasional use, and not when the plant is run every day and for a considerable poition 
of each day. The type and arrangement of condensing plant, the highest vacuum 
which can be economically obtained, and the extent to which condensing should be 
carried in any plant, are points which merit some consideration. 

The arrangement of the condensing plant may be either independent, that 
is, one condenser, air and circulating pump for each unit, or central, with a con¬ 
densing plant dealing with the exhaust from the whole station. The central system 

109 


ELECTRIC RAILWAY ENGINEERING 


has many advantages over the independent condensers ; the plant is concentrated, 
and therefore requires less attention, and the pumping machinery has a better 
efficiency owing to the larger capacity. 

The condensers for the central system should be in duplicate, each one of half 
the capacity of the station. This arrangement enables one condensing set to be 
shut down on light loads for overhaul or repair, and, in the event of a breakdown 
on one condenser, the whole station could be run on the other on a slightly impaired 
vacuum. 

Independent condensers should only be installed with large units, and when the 
output of the station is so great as to render a central condensing system unwieldy. 

The type of condenser depends entirely on the water supply. The types generally 
in use are the barometric, the jet and the surface condenser. If the station is situated 
near an abundant supply of cold water, the surface condenser gives the best results. 
The water of condensation, being free from impurities, can be pumped straight to the 
boilers without treatment, at a temperature within five degrees of that corresponding 
to the vacuum, while the low temperature of the cooling water also reduces the 
necessary cooling surface and thus enables the surface condenser to compare 
favourably with the barometric in point of cost. 

Where water is scarce it becomes necessary to cool the circulating water by 
means of cooling towers, in which case the inlet temperature of cooling water is some 
20 degrees F. higher than would be the case if the supply was drawn from a river, 
lake, or canal. The higher temperature of the inlet water necessitates a much larger 
quantity, and to reduce this quantity to a minimum and also to increase the efficiency 
of the cooling towers it is necessary that the water should leave the condenser as near 
the temperature of the steam as possible. The cooling water can be discharged from 
a barometric condenser within five degrees of the steam temperature at any vacuum 
or any inlet temperature, while, to obtain the same results from a surface condenser 
with high inlet temperature, the surface would have to be increased to an amount 
altogether prohibitive. Barometric condensers are, therefore, the most economical 
where cooling towers are used, as, the discharge from the condenser being as hot as 
possible, less water will be required, and the efficiency of the towers will be higher 
than with surface condensers. 

In determining the cooling surface and the quantity of water required for a 
surface condensing plant for any given vacuum, the all-important factor is the 
temperature of the cooling water. The quantity of water required may be reduced 
by a proportionate increase in the cooling surface ; the greater the cooling surface, 
the nearer the final temperature of the water will approach the temperature of the 
steam, and the reduced working expenses must be balanced against the extra first 
cost of the condenser to arrive at the most economical arrangement. In practice, 
however, it is seldom desirable to reduce the difference of temperature between the 
discharge water and steam to less than 15 degrees F., owing to the abnormal amount 
of cooling surface which would be necessary to obtain this result. The diagram 
shown on Fig. 110 has been prepared for the purpose of determining the quantity of 
surface and water necessary for any given vacuum and inlet temperature. The 
condenser should be designed so that the speed of water through the tube reaches or 
exceeds the critical speed at which the water is broken up, and the consequent 
transference of heat reaches a maximum. The speed should exceed 3 feet per 
second for tubes of 1 inch diameter. 

The diagram is based on a heat transference of 200 B.T.U. per hour per square foot 

i io 


THE ELECTRICAL POWER GENERATING PLANT 


of surface per degree difference of temperature for all temperatures. This figure will 
vary with the state of the surfaces and according to the amount of air present, and, 
although it has been shown by tests that this figure can be exceeded, even doubled, 
the figure given may be taken as the average for condenser tubes under ordinary 
working conditions. 

The vacua given in the diagram refer to the steam within the condenser. The 
presence of air in the condenser would cause the vacuum recorded on the gauge to be 
lower than that actually due to the steam, the difference depending on the effective 
volumetric capacity of the air-pump, so that about 97 per cent, of the vacuum given 
in the diagram would represent the gauge vacuum, the proportion varying according 
to the quantity of air present. 

Of the many conditions which are inseparable from condensing propositions, the 
two known conditions are usually the vacuum required and the temperature of 
the cooling water. 

The inlet water temperature is indicated on the left-hand side of the diagram by 
the diagonal lines ascending from left to right, and the difference of temperature 
between the outlet water and steam is shown by reverse diagonals. To ascertain from 
the diagram the quantity of water and surface required, follow the line corresponding 
to the known inlet temperature until the reverse diagonal corresponding to 15 degrees 
difference of temperature is reached. From this point ascend vertically to the curve 
corresponding to the vacuum, when the water required can be read to the left of the 
diagram. From the same point [i.e., where the diagonals cross) proceed horizontally 
to the line corresponding to the vacuum at the right of the diagram, when the 
necessary surface will be found at the bottom. It will be seen that, should the 
amount of surface thus obtained be prohibitive, it can be reduced and the quantity 
of water increased, by varying the difference of temperature and proceeding as 
before. 

For barometric condensers, the right-hand portion of the diagram is unnecessary, 
and, as the water can always be discharged at a temperature within 5 degrees of the 
steam, the necessary quantity may be found by following the line corresponding to the 
known inlet temperature up to the diagonal corresponding to 5 degrees difference, 
ascending vertically to the vacuum curve and reading to the left. 

The difference of temperature between the steam and the outlet water in a 
barometric condenser, depends upon the extent of water surface exposed to the steam, 
and the finer the division of water and the more efficiently the steam is mixed with it, 
the smaller will be the difference of temperature and the less water will be required. 
In the most efficient counter-current condensers, this difference can be reduced to 
5 degrees without increasing the size of the condensing chamber beyond the normal 
dimensions. 

For circulating the water, there is little to choose between a reciprocating and a 
centrifugal pump. The former has the advantage of greater efficiency, and the 
quantity pumped can be varied to suit the load. I he lattei is cheaper in fiist 
cost, its maintenance is practically nil, and it requires the minimum of attention. In 
the case of a barometric condenser the quantity of water thrown by the centrifugal 
pump is to some extent dependent on the vacuum, which necessitates speed adjust¬ 
ment, either automatic or otherwise, to prevent the quantity of watei pumped 
decreasing whenever the vacuum falls. In spite, however, of the relatively pool 
efficiency of the centrifugal pump and the disadvantages due to the lack of positive 
action, its use in connection with a barometric condenser is often desirable on account 


ELECTRIC RAILWAY ENGINEERING 


of its simplicity, cheapness, and low upkeep, and the special features of individual cases 
must decide the type of pump which should be installed. 

The air should be extracted from the vacuum chamber by means of an air-pump, 
of which there are two types in general use, viz., the dry air-pump, which extracts the 
air only from the condenser, and the wet pump, which deals with the air and water in 
one operation. The dry air-pump is usually double-acting, and the friction losses are. 
therefore, only half of those which occur in a single-acting wet air-pump, but, owing to 
clearance spaces, the efficiency of the dry air-pump falls off rapidly as the vacuum is 
increased until a point is reached at which the entire stroke of the pump is devoted to 
compressing the air into the clearance space without raising its pressure sufficiently 
to discharge it against the atmosphere; on the return stroke the air re-expands into 
the cylinder, and no effective work is done by the pump. The air extracted from the 
condenser, being separate from the water of condensation, may be cooled on its way to 
the pump, thereby reducing the volume to be dealt with and consequently increasing 
the effective work performed by the dry air pump. The wet air-pump is usually 
single-acting, and for that reason is made with three cylinders to increase the volumetric 
capacity. The clearance spaces are water-sealed, and therefore the effective work of 
this pump only ceases when the air has been rarefied to such an extent that the 
leakages through joints, glands, etc., balance the volumetric capacity of the pump. 
The volumetric efficiency of a dry air-pump depends mainly on the proportion of 
clearance to length of stroke, and at low vacua the loss due to clearance is compensated 
for by its cylinders being double-acting, and its efficiency at a low vacuum is greater 
than that of a wet air-pump, but with a high vacuum the superior volumetric efficiency 
of the wet air-pump, due to the absence of clearance spaces, considerably more than 
compensates for the fact that its cylinders are single-acting. It may be assumed 
therefore that the higher the vacuum the greater the advantage of the wet over the 
dry air-pump, but the point at which this advantage begins depends on the extent of 
clearance in the dry air-pump. 

If a wet pump is used in connection with a barometric condenser, cold water 
should be admitted to the suction in sufficient quantity to fill the clearance spaces, 
while in the case of a dry air-pump operating with a surface condenser an additional 
small pump is necessary to remove the water of condensation. 

The air which has to be removed from the condenser is due largely to the air 
pumped into the boiler with the feed water, and to leakage in the engine stuffing boxes, 
and at the various joints in the piping and vessels in which the vacuum is maintained. 

The presence of air tends to raise the pressure within the condenser, directly by 
reason of its own pressure being added to that of the steam and indirectly by retarding 
the transference or heat from the steam to the water. The reduction in the rate of 
heat transference due to the latter, necessitates a greater difference of temperature 
between the steam and water in order to condense the same amount of steam, and the 
temperature, and consequently the pressure, of the steam will therefore be raised until 
the difference of temperature is sufficient to transfer the necessary amount of heat 
against the resistance to heat transference due to accumulation of air. 

The quantity of air thus admitted into the condensing system varies greatly with 
different installations, and is much larger with reciprocating engines than with turbines, 
and the volumetric capacity of the air-pump must depend upon the quantity of 
air to be dealt with and the extent to which it is expanded. As the degree of air 
expansion is increased, and the air pressure reduced, the gauge vacuum will approach 
nearer to the vacuum corresponding to the steam temperature, but as finality in this 

112 


THE ELECTRICAL POWER GENERATING PLANT 


respect can never be reached, it becomes necessary to limit the vacuum efficiency, i.e., 
the ratio of gauge vacuum to that corresponding to steam, to a figure which can be 
obtained with an air-pump of reasonable dimensions. 

It will be seen that the quantity of air admitted must be assumed, but various 
trials of existing installations have shown that an effective air-pump displacement of 
1 cubic ft. per pound of steam condensed will give a vacuum efficiency of 98 per cent, 
while maintaining a gauge vacuum of 28 ins. of mercury. The above figures 
indicate that the amount of air admitted to the condensing system under the conditions 
mentioned, is about 0‘02 cubic ft. at atmospheric pressure for every pound of steam 
condensed, and if the air-pump displacement is assumed as above, the vacuum 
efficiency will vary with the extent of air leakage. 

It would appear at first sight that the barometric condenser would require an air- 
pump with a larger capacity than would be necessary for a surface condenser, but 
experience has shown that the air brought into the condenser by the cooling water is 
carried away down the barometric pipe by the velocity of the w T ater itself; in fact, with 
the requisite supply of cooling water, a vacuum of 28 ins. can be maintained in a 
barometric condenser working without an air-pump. The air-pump proposition is 
therefore the same for both surface and barometric condensers. 

Given equal conditions, the economical vacuum is much higher for a steam turbine 
than for a reciprocating engine, the economy in steam due to increased vacuum for 
the former being about three times as great as the steam economy of a modern 
reciprocating engine. This is partly accounted for by the leakage past the piston 
and valves of a reciprocating engine, and also cylinder condensation, increasing with 
the vacuum, while a steam turbine has no source of leakage which cannot be 
water-sealed. 

With large units, the steam consumption is reduced by about 1 lb. per kilowatt- 
hour for turbines and by about 0’35 lbs. per k.w.h. for modern compound reciprocating- 
engines for every inch increase in vacuum between 24 in. and 29 in. 

The economical vacuum is reached when the extra saving in steam due to any 
extra increase in vacuum is balanced by the cost of producing this increase, and as 
the quantity of water required for this purpose increases greatly with the inlet 
temperature, it follows that the chief factor in determining the economical vacuum is 
generally the temperature of the circulating water. There are so many conditions 
which indirectly bear on this question that it is impossible to lay down any definite 
rule applying to all cases, and in determining the most suitable vacuum the special 
features relating to each installation must be considered. 

The extent to which condensing should be carried is also affected by the desirability 
of not unduly reducing the temperature of the hot well, which in a properly propor¬ 
tioned condenser with an air-pump of ample displacement, will not differ materially 
from the temperature corresponding to the vacuum, and a portion of the plant should 
be run non-condensing in order to provide sufficient exhaust steam to raise the tempera¬ 
ture of the feed water from the hot-well temperature to 212 degrees l 1 ., that is to say, 
to the highest possible temperature at atmospheric pressure. Where the plant consists 
of a few large units, it is impracticable to apply this principle to the main plant, as 
the exhaust from one unit would be far in excess of the quantity necessary for 
feed water heating, and the loss of power due to atmospheric working would 
outweigh the benefits derived from raising the feed water temperature. llieie 
remains, however, the auxiliary plant, consisting of feed-pumps, air and circulating 
pumps, and, in the case of alternating current stations, exciter engines, and as 
E.R.E. I 13 1 


ELECTRIC RAILWAY ENGINEERING 


many of these auxiliaries should be steam-driven as will provide, with a margin 
for contingencies, sufficient exhaust steam to raise the temperature of the condensed 
water from the main plant, together with the make-up water, to 212 degrees F. 
The proportion of plant which should be used for this purpose will, of course, vary 
with the relative steam consumption of the main and auxiliary plants, but speaking 
generally, 1 i.h.-p. of auxiliary engines will be required to deal with the condensed 
water of 1G i.h.-p. of main plant when the vacuum is 26 ins., and for 14*5 i.h.-p. 
with the vacuum at 28 ins. 

At 212 degrees F. any scale-forming substance in the make-up water is deposited, 
hence the heater should take the form of a heater detartariser, in which the deposits can 
be conveniently dealt with, and in which the steam mingles with the water, and so 
ensures the maximum transference of heat. In view of the advantages derived by the 
scale being formed outside instead of inside the boiler, it is important that the feed 
water should be kept up to the atmospheric boiling point, and if, as is often the case, 
the exhaust from the whole of the auxiliary plant is insufficient for this purpose, live 
steam should be introduced into the heater in sufficient quantity to impart the 
necessary heat to the water. 

There are many varieties of apparatus in use for cooling the circulating water, all 
of which depend for their action upon the contact of water and air in motion. The 
apparatus which is mostly favoured, and which is generally found to be the most con¬ 
venient and suitable for ordinary installations, is the cooling tower, in which the water 
is pumped to a height of about 30 or 40 ft., and allowed to fall in drops, or in a film, 
over suitably disposed surfaces, the heat being extracted by the ascending current of 
air, the volume of which is dependent on the area of, and draught produced by, a 
chimney about 60 ft. in height. 

The temperature and humidity of the air entering and leaving the tower, and the 
temperature of the inlet and outlet water, are the conditions which determine the 
necessary water surface and the height of chimney, and as the former varies greatly 
in different seasons and localities, the cooling plant should be designed on a very 
liberal basis, and to meet the worst possible conditions. 

Heat is transferred from the water to the air by radiation, which raises the 
temperature of the air, and by evaporation, the latent heat for which is extracted from 
the remaining water. The transference due to radiation may be taken as 0’3 B.Tk.U. 
per hour per square foot of water surface per degree F. of mean difference of 
temperature between water and air, at a relative air and water velocity of 6 ft. per 
second, and this transference varies as the square root of the velocity. The heat 
given up by the water for evaporation, however, varies with the humidity and 
temperature of the air entering and leaving the cooling tower. The air on leaving 
the water is usually saturated to about 90 per cent, of the maximum saturation due to 
its temperature, and as the water necessary for completely saturating the air increases 
greatly as the temperature rises, it follows that the higher the outlet temperature of 
the air the greater the amount of heat transferred by evaporation for a given inlet 
temperature and humidity. On the other hand, the higher the outlet temperature of the 
air, the greater will be the amount of water surface necessary for radiating the balance 
of the heat to be transferred. A difference of temperature of 10 to 20 degrees 
between the outgoing air and the incoming water will be found to give an amount 
of surface which can be contained in a tower of reasonable dimensions. The outlet 
temperature of the air may be fixed by assuming a difference as above, and thus the 
amount of heat extracted from the water for 90 per cent, saturation of air at this 

1 14 


Lbs of wafer per tlo oP si earn 



10 II \Z 15 1+ 15 16 


Lbs, sfeom condensed per square foot of cooling surface per hour 

The vacua given above ore based on bororoefer of 29 92 inches of mercu r y , and are calculated for steam on l y; oHovooce should be made. 
for the presence of cur . 

The cooling surface is based on o heal - transference of 'SOO Rnfrsh Thermal Units per hour, per square fooC , per de g ree differe nc& of Vemp&r ature 
for all Omperofures This bein g the over o q e for condeo s er tubes under ordinary workin g conditions: ffor other rafes of transference 
tbe stream per sq ua re foot roust* be varied direc tly. 


Fig. 110. Diagram for estimating Condenser Capacities. 















































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































THE ELECTRICAL POWER GENERATING PLANT 

temperature may be ascertained, so that if this amount is added to the heat taken to 
raise the air temperature, and the sum divided into the total heat to be extracted, the 
total amount of air required is the result. Accepting 60 ft. as the height of chimney, 
and the density and volume of air required being known, the velocity of air and conse¬ 
quent area of chimney may be found by the application of well-known rules, and the 
an ways through the water surfaces should total rather more than the area of the 
chimney in order to avoid excessive resistance. The necessary surface can now 
be ascertained by applying the figure given above for transference of heat by 

It may happen that, owing to the low inlet temperature of the water to be cooled 
and the high prevailing atmospheric temperature and humidity, the necessary amount of 
water surface will be so great that the first cost and ground area required will render 
the size of tower thus obtained prohibitive. It will be seen that the cooling surface 
may be reduced by increasing the difference of temperature between the outlet air and 
inlet watei, but as this means a greater volume of air, and as the lower air temperature 
will reduce the draught produced by the chimney, it follows that the chimney height 
must be gieatly increased, or that the air must be forced through the tower by fans. 
It v ill be found impracticable to produce the desired result by increasing the height 
of chimney, and as the power consumed by fans is seldom justified by results, the 
vacuum should be reduced, and the consequent temperature of the water and the 
efficiency of the tower increased until the necessary size of tower is reduced to 
the proportions at which the first cost is justified by the saving in coal due 
to the resulting vacuum. 

If the w 7 ater passes in a film over plates or pipes, the amount of exposed water 
surface is, of course, equal to the total area over which it travels, but where the water 
is allowed to fall in drops, the tower should be designed so as to ensure that the water 
is divided up as finely as possible, and for proportioning the surface under such 
conditions it may be assumed that 300 gallons of water will expose 100 sq. ft. of 
surface when falling through a height of 32 ft. in the finest possible state of 
division. 

Having outlined the principles affecting the generating station equipment, the 
design of the individual apparatus, and their combination, these principles are 
best illustrated by reference to plants in actual operation, and we select for this 
purpose the following stations as being representative of large tramway and railway 
generating plants which have proved very successful from every point of view. 
I he conditions to be met in each case are sufficiently divergent to illustrate the 
application of the principles set forth in the early part of this chapter. The 
plants we select for our purpose are those of the Central London Railway Co., 
the Glasgow Corporation tramways, the Bristol tramways, and the Dublin United 
tramways. 

A special feature of the Central London Railway is the use of cooling towers for 
dealing with the circulating water for condensing. In the case of the Bristol tram- 
ways plant, owing to the limited space, the plant is arranged in storeys. In the case 
of the Glasgow Corporation tramways and the Dublin United tramways the 
conditions to be met are not exceptional, and the installations may be taken as 
representative of their class. 

Taking first the Central London Railway, the power-house (Figs. Ill and 112) 
is situated at the Shepherd’s Bush terminus of the Central London Railway. The 
building consists of a framing of steel work which supports the crane girders, coal 

i j 5 12 


ELECTRIC RAILWAY ENGINEERING 


bunkers, and roof trusses, the framework being filled in with brick walls 1 ft. 10J ins. 
thick. The floors of both engine and boiler rooms are constructed of steel joists filled 




in with concrete, and the roofs consist of boarding supported on wood purlins, the 
whole being covered with slates. 


116 










































































































































































































































































































































































































ii 7 


Central London Railway : Cross-section of Power Station. 




















































































































































































































































































































































ELECTRIC RAILWAY ENGINEERING 


Coal is brought on to the site by a siding from the Great Western and London 
and North-Western Railways, and is dumped from the trucks into a hopper situated at 
the end of the boiler room. The coal is fed from this hopper into a gravity bucket 
conveyer, which passes along the boiler room basement, up the end walls, and over 
the boiler room coal bunkers, from which the coal is supplied to the automatic 
stokers as required, by means of spouts. 

The boilers are arranged in eight batteries of two boilers each, four batteries 
being on each side of the boiler room, and the firing floor in the centre. 

The steam piping is arranged so that each battery of two boilers can supply one 
engine direct through an 8-in. pipe, and a branch is taken from each of these 
pipes into a 12-in. header, so that, if necessary, any engine may be supplied 
from any battery. 

Two lines of standard-gauge railway track are laid in the boiler room basement, 

and the ashes are run direct into trucks, which, after passing through a tunnel 

under the outside hopper, are hauled up an incline of about 1 in 24 to the general 

yard level. 

«/ 

The main flues are situated at the back of the boilers in the basement, and a 
fuel economiser is inserted in each flue, a by-pass being provided so that either flue 
may be turned through either economiser into either chimney. There are two brick 
chimneys, octagonal in shape, situated about 90 ft. from the end of the boiler 
room, and 44 ft. apart, and the firebrick lining in each is carried to a height 
of 40 ft. The economiser scraper gear and motors for driving same are situated 
in a chamber above the economisers and flues, between the boiler room and the 
chimneys, and at the level of the boiler room firing floor. 

The main generating sets are arranged three on each side of the engine room, 
leaving a clear floor space of 10 ft. in the centre of the engine room. The exhaust 
from the main engines is taken through 18-in. branches into a main 42-in. 
pipe, which passes along the centre of the engine room basement to the end of the 
engine room. It is then taken upwards to a height of 16 ft. above the engine 
room floor level, where, by means of a 42-in. tee piece, the exhaust steam is turned 
either right or left into duplicate oil separators and condensers. A 24-in. pipe 
provided with an automatic relief valve is taken from the top of the tee piece and 
continued up the engine room end wall above the roof to the atmosphere. 

The circulating water is drawn from three tanks, 23 ft. in diameter and 20 ft. 
deep, by three triple expansion pumps, the water being pumped into the bottom of 
either or both condensers. After passing twice through the condenser the water 
passes to the cooling towers and finally reaches the suction tanks. 

The Edwards air-pumps are situated at the end of the engine room, and dis¬ 
charge the water of condensation into a tank of 1,580 gallons capacity, from which the 
boiler feed-pumps draw their supply through a Venturi water meter. The make-up 
feed water is drawn from the circulating water on the discharge side of the con¬ 
densers, and the make-up for the circulating water is discharged into the cooling 
tower tank from an artesian well, the air compressor for this purpose being situated 
in the basement of the engine room. 

The oil is drawn from the separators by means of small oil pumps fixed to the 
end of the air-pumps and operated from the end of the air-pump crank shaft. 

Table XXXVa. contains a schedule of the type and capacity of the plant installed. 


i iS 


THE ELECTRICAL POWER GENERATING PLANT 


Table XXXVa. 

Schedule of Type and Capacity of Plant Installed at the Central London Railway 

Generating Station. 


Item. 


Main engines 


Number. 


Main generators 


Exciter engines 


Exciter generators 
Exciter motor . 

Exciter generator 


Lighting engines 


Lighting generators 
Transformers 

Rotary converter 

Condensers 

Air-pumps 
Circulating pumps 


1 

2 

2 

3 


Cooling towers 


Cooling towers 


Boilers 


2 

16 


Type. 


Size and Rating. 


Remarks. 


Horizontal cross 
compound con¬ 
densing, Corliss 
gear, 94 revolu¬ 
tions per minute 

Three - phase re¬ 
volving field type, 
5,000 volts, 25 
cycles per second 

Vertical tandem 
compound, 400 
revolutions per 
minute 

125-volt . 

Induction type, 
5,000 volts/ 290 
revolutions per 
minute 

125-volt . 

Vertical compound, 
400 revolutions per 
minute 

Continuous current, 
500 volts 

Three - phase, air¬ 
cooled, 5,000 volts 
to 300 volts 

Three - phase, 300 
volts A.C. to 500 
volts C.C. 

Vertical, open top 
surface condensers 


Edwards, three- 
throw, 130 revolu¬ 
tions per minute 
Worthington triple 
expansion 


Cylinders 23 ins. 
and 46 ins. in dia¬ 
meter x 48 ins. 
stroke, 1,2 50 
I.H.-P. 

Full load, 850 kilo¬ 
watts 


Cylinders 9J ins. X 
15 ins. diameter X 
6 ins. stroke, 75 

I.H.-P. 

Full load, 50 kilo¬ 
watts 

Full load, 200 H.-P. 


Full load, 120 kilo¬ 
watts 

Cylinders 8 ins. and 
14 ins. diameter 
X 7 ins. stroke, 
75 I.H.-P. 

Full load, 300 kilo¬ 
watts 

Full load, 300 kilo¬ 
watts 

Full load, 900 kilo¬ 
watts 

Cooling surface, 
9,000 sq. ft.; capa¬ 
city, 80,000 lbs. of 
steam per hour 
Cylinders 22 ins. 
diameter X 16 ins. 
stroke 

Steam cylinders 
6 ins. and 9 ins. 
and 16 ins. dia¬ 
meter X 15 ins. 
stroke; water 
cylinders, 20 ins. 
diameter X 15 ins. 
stroke 


Steam consumption 
on full load, 14'3 
lbs. of saturated 
steam, 150 lbs. 
pressure, and 26 
ins. vacuum. 

Efficiency at full 
load 95 per cent., 
at half-load 91 per 
cent. 


Driven by 35-H.-P. 
C.C. motor. 


Barnard Wheeler, 
with one pair of 
fans to each 

Klein towers . 

Babcock and Wil¬ 
cox 


Heating surface, 
3,580 sq. ft. to 
evaporate 12,000 
lbs. of steam per 
hour at 160 lbs. 
pressure 


Fans driven by 35- 
H.-P. engines at 
180 revolutions per 
minute. 


H9 












































ELECTRIC RAILWAY ENGINEERING 


Table XXXYa.— continued. 


Item. 

Number. 

Type. 

Size and Rating. 

Remarks. 

Stokers .... 

16 

Vickers . 

Grate area, 90 sq.ft. 

Driven by two 9J- 
H.-P. tandem com¬ 
pound engines. 

Economisers 

2 

Green’s patent 

768 tubes 

Scrapers driven by 
two 5-H.-P. motors. 

Feed-pumps 

3 

Direct-acting duplex 

Steam cylinders, 
12 ins. and 18 ins. 
diameter X 15 ins. 
stroke; 16,000 
gallons each per 
hour against 160 
lbs. pressure per 
square inch 


Water tanks 

2 

— 

20,000 gallons each • 


Coal conveyer . 

1 

Gravity bucket 

60 tons per hour 

Driven by 8-H.-P. 
motor. 

Coal bunkers 



1,000 tons capacity 



Coming next to the generating station of the Glasgow Corporation tramways, 
shown on Figs. 113 and 114, the generating station is situated in the northern district 
of the city, on the north bank of the Forth and Clyde Canal. The Caledonian and 
North British Railway Companies have sidings running over the outer storage hoppers. 

The building consists of a framing of steel work supporting the coal hoppers and 
conveyer, main flues, and economisers, crane runway girders, and roof trusses, and 
enclosed with brick walls. 

The firebrick lining in the chimneys is carried to a height of 150 ft., and varies 
in thickness from 18 ins. to 9 ins. 

The engine house and boiler house floors are constructed of rolled steel beams 
filled in with concrete. 

The main flues are supported on girders above the boilers, and enter the stacks 
at a height of 30 ft. above the boiler house floor. 

They are constructed of f-in. plating stiffened by steel angles. Branches con¬ 
structed in the same manner are taken off to the economisers, which are fixed above 
the main flue, a separate connection being made to the stacks; dampers are 
arranged so that the economisers may be bye-passed when necessary. The uptakes 
from the boilers to the flues are made of j-in. plate. 

The outside coal-handling arrangement consists of a bunker structure with two 
dumping tracks and eight hoppers for the high level line, and two dumping hoppers 
for the low level line. In addition to the coal dumping tracks on the high level line, 
a third track is laid between these two tracks to serve as a siding and for carrying the 
ashes from the ash shute outside the boiler house wall. 

The inside coal bunkers are arranged in the centre of the boiler house, and 
extend the full length of the boiler batteries. The side plating is j in. thick, and 
the bottom plating forming the hoppers is f in. thick. A bulkhead is arranged in the 
bunkers between each battery of boilers, the sides and bulkheads have stiffeners 
riveted to the plating 3 ft. apart, and each hopper is arranged with a 16-in. opening 
and valve at the bottom. 

The coal runs through valves provided in the hoppers of the outer bunkers to 

120 




















Fig. 113. Glasgow Corporation TRAMWA\ r s: Plan of Power Station. 










































































































































































































































































































































































































































































































































































































































































I 


THE ELECTRICAL POWER GENERATING PLANT 


the conveyer filler below, and is conveyed to the bunkers above the boilers, dumping 
levers being provided over each bunker, so that the buckets may be tipped at any 
one of these. 

Travelling ash fillers are provided in the basement, so that ashes may be run 
from the boiler ash-pits into the conveyer and transferred to the ash bunker at the 
end of the boiler house. This is periodically emptied by running the ashes through 
the spout into wagons on the siding outside the boiler house. 

Below the valve of the overhead bunkers are fixed hoppers of the self-contained 
trolley type, with shutes, and provided with a weighing scale. At the bottom of the 



shute is provided a balanced valve operated by a lever from the boiler house floor 
level, and from these shutes the coal is delivered into the stoker hoppers. 

The water supply for feed purposes is obtained from the Corporation mains 
through storage tanks, placed on girders between the stacks, the make-up water being 
supplied from these tanks through ball valves in the hot wells. The feed-pumps take 
their supply from the hot wells and deliver into a header in the engine house base¬ 
ment, which is connected up to each boiler feed ring, directly and also through the 
economisers. Each of the pump delivery branches to this header is provided with 
one feed-water filter (capacity 15,000 gallons per hour) and one water meter so 
arranged that either or both may be bye-passed. 

The boilers are arranged in eight batteries of two boilers each. 

The main steam piping consists of one main header, 16 ins. diameter, divided 
into two parts by means of expansion bends, which are provided with valves on each 
side for cutting off the steam. Each of the main parts of the header is further 
divided by 16-in. valves into two sections. Each of these four sections is connected 
to two batteries of boilers by two 9-in. pipes with 7-in. branches, and to one of the 
main engines by one 14-in. pipe for each of Nos. 1 and 2 engines, and a 15-in. pipe foi 

12 i 













































































































































































































































ELECTRIC RAILWAY ENGINEERING 


each of Nos. 3 and 4 engines. By this arrangement it is possible to supply steam 
from two boilers directly to the corresponding engine, or the header may be used in 
common by the boilers and engines. 

The auxiliary steam piping consists of a main range 10 ins. diameter con¬ 
nected to each end of the main steam header, and forming with it a complete ring; 
branches 7 ins. diameter are provided for the auxiliary engines, 3J ins. diameter 
for the exciter engines, and 2£ ins. diameter for the boiler feed-pumps. 

The exhaust piping between each main engine and its condenser, consists of two 
24-in. vertical pipes, with bends bolted up to the exhaust branches on the two low- 
pressure cylinders of the engines, these two pipes being connected by means of bends 
and tees into a 30-in. pipe carried to the condenser; connection is also made 
through a stop valve and an automatic relief valve to the atmospheric exhaust pipe, 
which varies in diameter from 34 to 40 ins. 

The auxiliary exhaust piping consists of one main range, 18 ins. diameter, 
connected up to the main exhaust piping through an 18-in. stop valve and automatic 
relief valve by a reducing pipe 18 ins. to 34 ins. diameter. 

Between exciters 4 and 5 the diameter of the piping is reduced to 8 ins. 
diameter. Branches 14 ins. diameter are provided for the exciter engines, and 
3 ins. diameter for the feed-pumps. 

The air-pump discharge piping consists of a 14-in. main range running between 
the air-pumps and the hot wells, with 10-in. branches to the main air-pumps, 
8-in. to the auxiliary pump, and 14 ins. diameter to the hot wells. 

The suction piping from the canal to each main circulating pump is 15 ins., 
and for the auxiliary pump 10 ins. diameter, provided with foot valves and strainers at 
the canal intake. 

The main discharge varies from 24 ins. to 30 ins. diameter, with 15-in. branches to 
the main condenser and 10-in. to the auxiliary condenser. 

Blow-down piping from the boilers and economisers, drain piping from the tanks, 
hot wells, etc., are also provided, together with the piping and steam traps for efficient^ 
draining the main and auxiliary steam piping. 

The switch gear is designed to control the operation of four three-phase generators, 
together with the exciters, and for the distribution to five sub-stations of the following 
capacities:—2,500, 2,000, 1,500, 3,500, and 2,500 kilowatts. 

The sizes and types of the various items of plant are given in Table XXXYb. 

Table XXXYb. 


Schedule of Type and Capacity of Plant Installed at the Generating Station of the 

Glasgow Corporation Tramways. 


Item. 

Number. 

Type. 

Size and Rating. 

Remarks. 

Main engines 

2 

Vertical three- 
cylinder com¬ 
pound condensing, 
75 revolutions per 
minute 

Cylinders 42 ins. 
and 60 ins. and 
60 ins. X 60 ins. 
stroke ; full load, 
4,000 I.H.-P. 


Main engines 

2 

Ditto ditto 

Cylinders, 42 ins. 
and 62 ins. and 
62 ins. X 60 ins. 
stroke ; full, load, 
4,000 I.H.-P. 


Main generators 

4 

Three-phase revolv¬ 
ing field type, 
6,500 volts, 25 
cycles per second. 

Full load, 2,500 kilo¬ 
watts. 



I 22 















THE ELECTRICAL POWER GENERATING PLANT 


Table XXXYb.— continued. 


Item. 

Number. 

Type. 

Size and Rating. 

Remarks. 

Auxiliary engines 

2 

Vertical cross com¬ 
pound condensing, 
Corliss gear, 90 
revolutions per 
minute 

Cylinders 22 ins. 
and 44 ins. dia¬ 
meter x 42 ins. 
stroke ; full load, 
800 I.H.-P. 


Auxiliary generators . 

2 

Continuous-current 
compound-wound, 
500 to 550 volts 

Full load, 600 kilo¬ 
watts 


Exciter engines . 

2 

Vertical compound 
condensing, 300 
revolutions per 
minute 

Cylinders 11 ins. 
and 19 ins. dia¬ 
meter X 8 ins. 
stroke ; full load, 
85 I.H.-P. 


Exciter generators 

2 

Shunt-wound . 

Full load, 50 kilo¬ 
watts 


Main condensers 

4 

Horizontal type sur¬ 
face condensers 

Cooling surface, 
7,000 sq. ft.; capa¬ 
city, 60,000 lbs. of 
steam per hour 


Main circulating pumps . 

4 

Centrifugal 

240,000 gallons of 
water per hour 

Driven by 55-H.-P. 
motor. 

Main air-pumps 

4 

Edwards, three- 
throw, 150 revolu¬ 
tions per minute 

Cylinders 16 ins. 
diameter, 12 ins. 
stroke; capacity, 
60,000 lbs. of con¬ 
densed water per 
hour 

Driven by 27-H.-P. 
motor. 

Auxiliary condenser . 

1 

Horizontal type sur¬ 
face condenser 

Cooling surface, 
2,800 sq. ft. ; capa¬ 
city, 24,000 lbs. of 
steam per hour 


Auxiliary circulating pump 

1 

Centrifugal 

96,000 gallons of 
water per hour 

Driven by 25-H.-P. 
motor. 

Auxiliary air-pump . 

1 

Edwards, three- 
throw, 150 revolu¬ 
tions per minute 

Cylinders 11 ins. 
diameter, 9 ins. 
stroke; capacity, 
24,000 lbs. of con¬ 
densed water per 
hour 

Driven by 12-H.-P. 
motor. 

Boilers .... 

16 

Babcock and Wil¬ 
cox 

Heating surface, 
5,173sq.ft.; super¬ 
heater surface, 452 
sq. ft. ; capacity, 
20,000 lbs. of steam 
per hour at 160 lbs. 
pressure 

Driven by four 
motors of P2-H.-P. 

Stokers .... 

16 

Babcock and Wil¬ 
cox chain grate 

Grate area, 76 sq. ft. 

Economisers 

2 


Capacity of each, 
12,000 gallons per 
hour, raised from 
90° to 160° F. 


Feed-pumps 

4 

Three-throw single- 
acting, 45 revolu¬ 
tions per minute 

Plungers, 6 ins. 
diameter ; capa¬ 
city, 8,000 gallons 
of water per hour, 
against 180 lbs. 
pressure 


Water tanks 

2 

— 

Capacity of each, 
18,000 gallons 


Coal conveyers . 

2 

Gravity bucket 
type 

Capacity, 50 tons 
per hour each 


Coal bunkers 

— 


Capacity, 5,400 tons 



123 
































ELECTRIC RAILWAY ENGINEERING 


We shall next describe the power station of the Bristol tramways (Fig. 115). This 
is interesting partly because it is built in storeys owing to the limitations of the ground 
at disposal. 

The power house is situated at approximately the centre of the tramway system. 
The site adjoins the Floating Harbour and St. Philip’s Street. An ample supply of 
condensing water can he obtained, and the facilities for the delivery of coal by means 
of barges are satisfactory. 

Owing to the limited space, it was found necessary to arrange the boiler room 
above the engine room, and the concentration of the loads on a small area which 
resulted from this arrangement, together with the unsatisfactory nature of the soil, 
necessitated special precautions in designing the foundations. 

The whole of the framing and walls of the power house, together with the stack, 
coal storage tank, and harbour wall, are supported on pitch pine piles 12 ins. to 14 ins. 
square, and about 30 ft. long. 

The main columns are built up of Z bars and plates, the overall dimensions being 
20 ins. X 15 ins., and the sectional area 80 sq. ins. 

Brackets are provided at a height of 36 ft. for supporting the crane runway girders. 

The boiler house floor is at a height of 44 ft. above the engine room floor, and is 
carried by rolled beams supported by girders 5 ft. 6 ins. deep with flanges 16 ins. x 
2 ins., which in turn are supported on the main columns. 

At the boiler house floor the dimensions of the main columns are 12^ ins. x 104 ins. 
and 25 sq. ins. area. These serve to support the main girders (5 ft. deep, flanges 
16 ins. x 1^ ins.) carrying the coal bunkers, water tanks, flue, and economiser. The 
main columns for supporting the roof above this level are of 9 ins. X 4J ins. I section. 

The coal hunkers are constructed with sides of ^-inch plating with stiffeners 3 ft. 
apart. The bottom plating forming the hoppers is f in. thick. A 16-in. opening is 
provided to each hopper, to which is fixed a balanced valve. The coal storage tank 
consists of a circular shell of steel plating, the bottom being funnel-shaped and provided 
with an opening and valve. 

The stack is constructed of steel plating varying in thickness from f in. to j in. 
The diameter at the top is 10 ft. 9 ins. ; this increases gradually to 14 ft. at 25 ft. 
from the base ; from this point it flares out to 20 ft. at the base. 

The lining of firebrick varies in thickness from 9 ins. to 4^ ins., the bricks being 
specially made to the radius required. 

The plating is riveted at the bottom to the cast iron base, which is anchored 
down to the brick base by means of eight 24-in. bolts. This brick base is 60 ft. high, 
and contains the stairway for giving access to the boiler house. 

The flue, which enters the steel stack at a height of 12 ft. from the base plate, is 
constructed of steel plating 4 in* thick, stiffened by steel angles, and lined through¬ 
out with firebrick. The economiser is fixed at the side of the flue near the stack end, 
and dampers are provided so that the economiser may be cut out of service for repairs. 

The coal is hoisted from the barges by means of the Hunt automatic shovel, into 
the Avery weigher at the top of the outside storage tank, into which it drops after the 
weight has been automatically recorded. The bottom of this tank is of a funnel shape, 
a valve being provided at the opening to regulate the flow of coal into the filler of the 
Hunt conveyer, which transfers the coal to the bunkers above the boilers. The conveyer 
returns through a trough below the boiler house floor, and openings are provided 
through which the ashes may he shovelled into the conveyer for conveyance to the ash 
tank, above which the buckets pass on their return to the coal filler below the storage 

124 



115. Bristol Tramways: Cross-section of Power Station. 

125 


Fk 






















































































































































































































































































































































ELECTRIC RAILWAY ENGINEERING 


tank. The conveyer thus serves both purposes at the same time. The ash tank is pro¬ 
vided with a valve and spout, by means of which the ashes can be run out into barges. 

The water supply for feed purposes is obtained from the city mains. Owing to 
its hardness, a water softener was installed to obviate boiler troubles due to deposit in 
the tubes. 

The feed-pumps take their supply of water from the storage tanks above, and 
deliver through the economiser into a duplicate system of piping provided with 
branches to each of the boilers. 

The boilers are arranged in four batteries of two boilers each. Steam is conveyed 
directly from each battery to the main header in the engine room, from which there 
is a branch to each engine. This header is divided by a valve into two sections. There 
is in addition a duplicate header in the boiler room to which each battery is 
connected, and by means of which it is possible to supply steam from any of the 
boilers, whilst part of the engine room header may be out of service for repairs. 

A connection is made to each end of the engine room header for a supply to the 
auxiliary plant. This forms a ring system, so that steam may be taken from either end 
of the header. 

The exhaust piping is so arranged that any of the engines can exhaust to either 
condenser, and as one condenser, with its circulating pump and air-pump, is capable 
of dealing with the total load, repairs can always be effected without exhausting to the 
atmosphere. 

The air-pumps deliver into a hot well in the basement, from which the water is 
drawn by the three-throw pumps and forced through Railton and Campbell filters up 
to the storage tanks. The additional water required to make up losses, etc., is supplied 
from the water softener through a ball valve in the hot well. 

The steam piping, etc., is all drained in an efficient manner by means of Geipel 
steam traps, the condensed water being led away to the hot well. 

The switchboard is situated on a gallery at the end of the engine room at a height 
of 12 ft. from the floor. 

The schedule in Table XXXVc. contains types and sizes of plant installed in this 
station. 


Table XXXVc. 


Schedule of Type and Capacity of Plant Installed at the British Tramways Generating 

Station. 


Item. 

Number. 

Type. 

Size and Rating. 

Remarks. 

Main engines 

4 

Vertical cross-com¬ 
pound condensing, 
Corliss gear, 90 
revolutions per 
minute 

Cylinders 22 ins. 
and 44 ins. dia¬ 
meter X 42 ins. 
stroke, 8001.H.-P. 


Main generators 

4 

Continuous current 
compound-wound, 
500-550 volts 

Full load, 550 kilo¬ 
watts ; overload, 
25 per cent, for 

2 hours 

Efficiency: full 
load,94 - 5 per cent ; 
half-load, 94 per 
cent.; quarter-load, 
91 per cent. 

Auxiliary engines 

2 

Vertical compound, 
400 revolutions 
per minute 

Full load, 75 I.H.-P. 

Auxiliary generators 

2 

Continuous current 
compound-wound, 
500-550 volts 

Full load, 50 kilo¬ 
watts 



126 




















THE ELECTRICAL POWER GENERATING PLANT 


Table XXX Vc.— continued. 


Item. 

Number. 

Type. 

Size and Rating. 

Remarks. 

Motor generators 

3 

Motor 5 00-volt 

50 kilowatts. 




shunt - w 0 u n d 
Generator, series 
wound 



Condensers 

2 

Horizontal type sur- 

Cooling surface, 




face condensers 

3,200 sq. ft. 


Air-pumps .... 

2 

Vertical twin type 

Steam cylinders 





7J ins. diameter 
by 8 ins. stroke ; 
pump cylinders 
17 \ ins. diameter 


Circulating pumps 

2 

Centrifugal 

— 

Driven by 29-H.-P. 





motors. 

Lift pumps 

2 

Three-throw, single- 

Plungers, 6J ins. 
diameter, 8 ins. 

Driven by 15-H.-P. 


acting 

motors. 




stroke 


Boilers .... 

8 

Babcock and Wil- 

Heating surface, 




cox 

3,140 sq. ft. ; 8,250 
lbs. of steam per 
hour at 150 lbs. 





pressure 


Stokers .... 

8 

Vickers type . 

Grate area, 45 sq. ft. 


Economiser 

1 

Green’s patent 

360 tubes 


Feed-pumps 

3 

Vertical compound 

Steam cylinders 




duplex 

5 ins. and 10 ins. ; 
water cylinders 

5 ins. diameter X 
10 ins. stroke 


Water tanks 

2 

— 

6,000 gallons each 


Water softener . 

1 

Tyacke patent 

3,000 gallons per 





hour" 


Coal conveyer . 

1 

Gravity bucket type 

60 tons per hour 

Driven by 15-H.-P. 



motor. 

Coal hoist .... 

1 

Hunt automatic 

60 tons per hour. 




shovel 


Coal bunkers 

— 


800 tons capacity. 



We shall now describe the power station of the Dublin United Tramways, 
illustrated in Figs. 116, 117 and 118. 

The generating station is situated at Ringsend, adjacent to the Grand Canal 
Dock, and is built upon hard gravel and blue clay. The building is composed of a 
steel framework, enclosed with brickwork, and rests on heavy concrete foundations. 
Two main bays, one housing the boilers and coal storage, and the other containing 
the generating and distributing machinery, are separated by a party wall, the engine 
room being 80 ft. and the boiler room 76 ft. wide. The entire building is above 
ground, the engine room floor level being 12| ft. above the general ground level, thus 
ensuring ample light and ventilation. 

The coal is taken from barges at the quay side by a grab suspended from a hoisting 
tower. The grab, which holds one ton, lifts the coal and drops it into a small truck, 
which, after being automatically weighed, travels down an incline, and dumps the coal 
at a predetermined point into the coal store, of 800 tons capacity, adjoining the end 
of the boiler room. From this store the coal drops into a gravity bucket conveyer, 
and is delivered to the coal bunkers, of 1,200 tons capacity, situated above the central 
space between the two ranges of boilers. The whole series of operations is automatic, 
and a minimum of attention is required. 


127 
















128 


Dublin United Tramways: Cross-section of Power Station. 











































































































































































































































































































































;rrT?T 


T. 




15hj53% 


mmrM 


117 Arrangement of Boiler Plant of Dublin United Tramways Generating Station 





























































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































• -• 






















































■ 





























































THE ELECTRICAL POWER GENERATING PLANT 

The boileis are arranged in six batteries of two boilers each, three batteries being 
ranged on each side of the boiler room. They are of the Babcock and Wilcox water 
tube type, with steam and water drums 36 ins. diameter, and 21 ft. 4 ins. long, 

and are fitted with automatic stokers, operated by a driving shaft beneath the boiler 
room floor. 

The gases leaving the boilers are conducted by means of two flues, one each side 
of the boilei house, to the economisers, situated on either side of the outside coal 
store, and finally to the two chimneys. These chimneys are of steel plate, with fire¬ 
brick lining, and rest on brick bases, octagonal in shape. They are 230 ft. in height, 
with an inside diameter of 10 ft. 

Hie steam piping is arranged so that one battery can supply one engine direct, 
forming an independent unit, while the main steam header enables the boilers and 
engines to be interchanged. 

ihe main engines are vertical cross-compound condensing and direct coupled 
to 500-kilowatt generators, and the units are arranged in rows, with ample floor space 
in the centre of the engine room. 

Iheie aie three surface condensers situated in the centre of the engine room 
basement, each condenser being between the foundations of two main units, and 
capable of dealing with the exhaust steam from both. These condensers are 
provided with combined steam-driven air and circulating pumps, and are all inter¬ 
changeable, thus facilitating the combination of any two generating sets with either con¬ 
denser. The feed-pumps, two in number, are of the vertical duplex tandem compound 
type, and each is capable of dealing with the whole of the necessary feed water, which 
is pumped through a feed water heater and duplicate filters on its way to the boilers. 
This heater takes the exhaust from the feed-pumps, air and circulating pumps, and 
the small stoker engines, and the water of condensation is drained into a cylindrical 
hot well, which also receives the air-pump discharge and clean steam drains. The 
level in the hot well is maintained by a make-up supply from the circulating discharge, 
and thus provides a continuous supply of hot feed water. 

The engine room is equipped with a 25-ton overhead crane, electrically operated by 
three separate motors, which are controlled from a cage suspended from the bridge 
girders. The cage is situated so that the operator has a clear view of the engine- 
room. The hoisting speed of the crane is from 4 to 50 ft. per minute, according 
to the weight, and the travelling speed is 60 ft. per minute in both directions. The 
switchboard is situated at the permanent end of the engine room, on a gallery 16 ft. 
from the engine room floor, and is approached by means of two iron staircases. 

The switchboard extends almost the entire width of the engine room, sufficient 
space being left on either side for access to the back of the board and to the offices. 
The panels comprising the board are bolted to suitable sustaining angle irons by 
nickel-plated bolts. 

At the back of the switchboard, and in three storeys, are situated the store rooms, 
workmen’s quarters, and various offices for engineers and switchboard attendants, the 
whole being well equipped with lavatories, bath-rooms, etc. The entire power- 
station and outside coal-handling apparatus is thoroughly well lit by an elaborate system 
of arc lighting and incandescent lamps. 

A schedule setting forth the types and sizes of the plant installed, is given in 
Table XXXVd. 


E.R.E. 


129 


K 


ELECTRIC RAILWAY ENGINEERING 

Table XXXYd. 

Schedule of Type and Capacity of Plant Installed at the Generating Station of 

the Dublin United Tramways Co. 


Item. 

Number. 

Type. 

Size and Rating. 

Remarks. 

Main engines . . . 

6 

Vertical cross-com¬ 
pound condensing, 
Corliss gear, 90 
revolutions per 
minute 

Cylinders 20 ins. 
and 40 ins. X 42 
ins. stroke, 800 
I.H.-P. 

Steam consumption 
at full load, 13 - 25 
lbs. per I.H.-P. 
saturated, 150 lbs. 
pressure, 27 ins. 
vacuum. 

Main generators 

6 

C.C. 500 volts 

Full rated load, 550 
kilowatts 

Efficiency : full, 94 
per cent. ; half, 95 
per cent.; quarter, 
93 per cent. 

Boosters .... 

3 

500 volts motor, 30 
volts generator 

15 kilowatts 


Boosters .... 

1 

Ditto ditto 

24 kilowatts 


Condensers 

3 

Horizontal surface 

2,400 sq. ft. 

Combined and 
driven by tandem 
steam engine cylin¬ 
ders, 7 ins. and 14 
ins. 

Air-pumps.... 

3 


16 ins. diameter, 16 
ins. stroke 

Circulating-pumps . 

3 


18 ins. diameter, 16 
ins. stroke 

Ditto ditto. 

Feed-pumps 

2 

Vertical duplex tan¬ 
dem compound 

8,000 gallons per 
hour, 5 ins. and 
10 ins. X 10 ins. 
stroke 


Travelling crane 

1 

Electrical overhead 

25 tons 


Boilers .... 

Stokers .... 

12 

12 

Babcock and Wil¬ 
cox water tube 
Vickers 

2,530 sq. ft. 


Conveyor .... 

1 

Gravity bucket 

50 tons per hour 

10 H.-P. motor- 
driven. 

Shutes .... 

6 

Weighing an d 
travelling 

8 cwt. capacity 


Hoisting tower . 

1 

Steam-driven grab 

40 tons per hour 


Economisers 

2 

Green’s patent 

! 192 tubes each 

Motor-driven scrapei 
gear. 


Although giving good results, and possessing individual features contributing to 
high overall efficiency, none of the stations described embody all the details or fulfil 
all the conditions set forth earlier in this chapter as necessary to obtain the best 
possible results. This is chiefly due to the location of these stations being such as to 
preclude the greatest advantages being obtained. Lack of a natural supply of cooling 
water in one case, restricted ground area in another, and the fact that they have all 
been in service a good number of years, tend to limit the efficiency of the power 
stations described. 

Figs. 119 and 120 illustrate a turbine power station designed on the principles 
already outlined, and may be taken as representing, both in arrangement and detail, 
the best practice in modern central station design. 

This station is equipped with five 2,000-kilowatt turbines of the vertical type, and 
supplied with steam at 150 lbs. pressure and 200 degrees superheat from ten marine 
type, water-tube boilers. 

The condensers are of the barometric jet type in duplicate, each set taking care 

130 


























119. Design of 10,000-k.w. Powek Station. Plan. 







































































































































































































































































































































































































ELECTRIC RAILWAY ENGINEERING 


of half the station. The water is circulated by centrifugal pumps, and the air 
extracted by single-acting three-throw wet air-pumps. 

The feed water passes from overhead storage tanks through heater detartarisers 
on its way to the feed-pumps, and is raised to the atmospheric boiling point by the 
exhaust steam from the auxiliaries. 

The feed-pumps are situated with a head on the suction side, thus enabling them 
to deal with the water at this temperature. 

The coal is handled automatically by gravity conveyors ; the boilers are provided 
with automatic stokers, and the ashes are removed from the boiler room basement in 



Fig. 120. Design of 10,000-k.w. Power Station. Cross-section. 


trucks. The turbines maintain a low steam consumption over a wide range, the 
piping throughout is of the simplest nature, and a vacuum of 28 ins. is maintained. 

Dealing next with the cost of operating and maintaining a generating station 
plant, we propose setting forth the working costs of a number of power stations, first as 
recorded and in the next place in such a manner as to enable an absolute comparison 
to be made. It is not an easy matter in making comparison between the returns of 
working of different power stations to obtain a common basis for comparison. The first 
difficulty one encounters is with regard to the cost of coal. The cost is given usually in 
pence per kilowatt hour, and it is seldom that the average price per ton paid for the coal 
is mentioned. Another difficulty arises out of the uncertainty as to the meaning of 
the term “ units generated.” This ambiguity arises from the use in some cases of 

i3 2 






















































































































































































THE ELECTRICAL POWER GENERATING PLANT 


electiicity for running a part or the whole of the auxiliary plant, and from inclusion in 
the total by some, and exclusion by other engineers, of the energy so used when 
computing the cost per unit. Where the energy used for auxiliary purposes is 

included, it precludes a fair comparison with other stations where the auxiliary plant 
is steam-driven. 

In the following tables we have, from the total energy generated, deducted all energy 
used m the power house for auxiliary purposes, including excitation where necessary, and 
haie adopted the term energy issued out of power station,” as conveying this meaning 
without ambiguity, so that it is clear that comparisons of the working expenses of 
different power stations are made on the same basis. Table XXXYI. gives the operating 
cost of the plants already described. 


Table XXXYI. 


Operating Costs of Electrical Power Generating Stations. 


Total kilowatt hours generated per annum 
>) >> used in power station 

>> >) issued out of power station 

Total coal consumed, tons 


Coal per kilowatt hour (issued from station), pounds 

” ” >• pence 

C ost of coal per ton shillings 


Cost in pence per kilowatt hour issued:-- 
Operation : 

Salaries and wages .... 

Fuel ....... 

Water ...... 

Oil, waste and stores .... 

Eepair and maintenance : 

Material and wages .... 


Total . 


Glasgow 

Corporation 

Tramways. 

Central 

London 

Railway. 

Dublin 

United 

Tramways. 

28,918,863 

18,552,546 

8,624,125 

919,488 

612,762 

147,354 

23,000,512 

17,939,784 

8,476,771 

35,267 

29,225 

16,488 

3-43 

3"65 

4-36 

0-12 

0-317 

0-226 

6-52 

16-25 

9-68 

0T04 

0-088 

0-123 

0-120 

0-317 

0-226 

0-008 

0-0012 

0-007 

0-014 

0-0140 

0-016 

0-036 

0-0460 

0-033 

0-282 

0-4662 

0-405 


TV e now present a series of tables in which an absolute comparison is made of the 
working of various plants differing in magnitude and in the extent, of use and setting 
forth in each case the overall efficiency of the plant in terms of the energy contained 
in the coal, the efficiency being defined as the ratio of the energy issued out of the 
power station to the energy contained in the coal. 

The following table (XXXVII., on p. 134), is a comparison of the overall efficiency 
of three of the plants described, and inasmuch as the plant is in each case of the saine 
class, the comparison is a valuable one. 

It will be noted that the overall efficiency increases with the magnitude of the 
plant owing to the higher efficiency of the larger units. In order to determine 
approximately the law of efficiency in this respect, we have analysed the returns of a 
large number of stations both in this country and in other countries. 

Twenty-six of these stations are classified in three groups in Table XXXVIII. 
on pp. 136 and 137. In each group, one-half represents British stations, and one- 
half represents stations outside of Great Britain. Two considerations controlled the 
choice of stations for inclusion in the investigation. The first consideration was 
that the available data should include as many as possible of the facts affecting the 

133 































ELECTRIC RAILWAY ENGINEERING 


annual overall efficiency ; the second consideration was that the range of capacities 
and the average capacity of the British stations should be about equal to the range of 
capacities and the average capacity of the stations located outside of Great Britain. 
This selection was made without any reference whatever to the value of the resulting 
average efficiencies. 

Table XXXVII. 


Annual Overall Efficiencies of Three Electrical Power Generating Stations. 


Installation. 

Glasgow 

Corporation 

Tramways. 

Central 

London 

Railway. 

Dublin 

United 

Tramways. 


1905. 

1905. 

1905. 

Total rated capacity (kilowatts) ...... 

11,200 

5.100 

3,600 

Kilowatt hours generated per annum ..... 

23,918,863 

18,552,546 

8,624,125 

„ ,, issued out of power station per annum . 

23,000,512 

17,939,784 

8,476,771 

Maximum output, kilowatts ....... 

8,520 

5,000 

3,000 

Load factor .......... 

32 

41-4 

32-2 

Coal consumed, tons ........ 

35,267 

29,225 

16,488 

Calorific value (B.T.U.) per lb. ...... 

12,600 

14,500 

12,500 

,, „ kilowatt hours per ton ..... 

8,270 

9,540 

8.230 

Kilowatt hours input per kilowatt hour output 

12-65 

15-5 

16 

Annual overall efficiency ........ 

79 

6-4 

6 25 

Coal cost per ton, shillings ....... 

6-52 

16-25 

9-68 

Cost of coal per kilowatt hour of calorific value, pence . 

0-00949 

0-0204 

00141 

Final cost of electrical energy per kilowatt hour of output, pence 

0 12 

0-317 

0226 


The table gives the output of the station for the period considered, in millions of 
kilowatt hours per annum. The stations are arranged in the order of their annual 
outputs. In the table are also compiled those particulars of each station which could 
be expected to have a bearing upon the overall efficiency, together with the data 
necessary for calculating this overall efficiency. The annual input of energy in the 
form of the energy of combustion of the coal, the annual output in millions of kilowatt 
hours of electrical energy, and the annual overall efficiency are likewise recorded for 
each of the twenty-six stations. 

In Table XXXIX. these results are averaged for the British stations and for the 
stations situated outside of Great Britain. 

Table XXXIX. 


Annual Overall Efficiencies of English and Foreign Electrical Generating Stations. 


Class. 

Great Britain (B) 
or Abroad (A). 

Average Output from 
Generating Station 
during Year in 
Millions of Kilowatt 
Hours. 

Average Efficiency of 
Generating Station 
in per cent. 

Between 0-9 and 3"3 millions of kilowatt ( 

B 

2-0 

2-8 

hours per year . . . . . ( 

A 

1-9 

5-2 

Between 6 and 13 millions of kilowatt ( 

B 

9-3 

5-8 

hours per year . . . . . ( 

A 

9-9 

6*6 

Between 18 and 45 millions of kilowatt j 

B 

28-8 

7-2 

hours per year . . . . . ( 

A 

32-6 

8-3 


In Fig. 121 these average results are plotted in the form of curves showing the 
annual overall efficiency of the generating stations as a function of the millions of 
kilowatt hours of annual output. 


134 

































THE ELECTRICAL POWER GENERATING PLANT 

It is to be regretted that the published returns from generating stations are not 
more complete.. Thus we naturally ask ourselves whether it might not be possible to 
trace a connection between the overall efficiency and the extent to which electrical 
storage batteries are employed, but we find that the incompleteness of our data makes, 
this impossible. It is fair to assume that all these stations were operated condensing 
although this fact is recorded only in the case of the British stations. In fact, 110 m 
condensing stations, when known to be such, were purposely excluded from the 
comparison. In no case, however, are there records of the average vacuum main¬ 
tained, nor of the average amount of superheat employed. The comparison of the 
capital cost and the rate of depreciation would also have been impracticable, owing to 
the insufficiency of the published data, and hence one cannot assert conclusively that 
the one or the other set of generating stations represents the better engineering. 

It is, hovei ei, quite evident that even the better of the two efficiency curves of 
Fig. 121 is very low. The efficiency of steam generating sets at full-load frequently 



Fig. 121. Comparison of Efficiencies of English and Eoreign Electrical 

Generating Stations. 

exceeds 20 per cent, in larger sizes, and the efficiency of a good boiler working at its 
rated capacity should not fall below 75 per cent. Taking the efficiency of the steam 
piping at 95 per cent., there is obtained a practicable full-load overall efficiency of the 
generating station of 0'20 x 075 x 095 = O'14. 

The difference between this efficiency and that actually obtained in practice, is due 
chiefly to the circumstances that the plant is run for a large part of the time at 
considerably less than full load, that fires must be kept under one or more spare 
boilers, that the boilers and engines are not maintained in the condition of highest 
efficiency, that the supply of air to the fires is not suitably regulated, that the coal 
is not uniformly of the calorific value of the samples tested, and to various other detail 
circumstances. 

As shown in Table XXXIX., it is not unusual to find large stations with an 
annual overall efficiency of over 7 per cent. 


135 












































ELECTRIC RAILWAY ENGINEERING 



£ 60 







rQ 


6 

|r os 

5 ci 

-4-i — 13 

C 

S5 si, 

U 

O 

/**N 

c .p 

7? -*- 3 

Class. 

CS 03 
$ G j_, 

c - 03 
^ c P. 

^ 0 . 

0 

0 - 3 ^ 

ndensing or 
condensini 

iish Station 
Abroad (A 

mulators en 
not in Gene 
Station. 


c 

5 

'u 

P3 

O O 











CO 

0-95 

Not stated 

A 

Accumulators 

O 



employed 

0-97 

Not stated 

A 

Accumulators 




employed 

ci 

1-00 

Condensing 

B 

Not stated 

C 

B 

1-09 

Condensing 

B 

Not stated 

1-18 

Not stated 

A 

Accumulators 

K • 




employed 

0 5? 

1-33 

Condensing 

B 

Accumulators 




employed 

E S-, 

2'07 

Not stated 

A 

Accumulators 

? 8 , 




employed 

cb 

2-25 

Condensing 

B 

Accumulators 

'C 



employed 


2-90 

Condensing 

B 

Accumulators 

0 



employed 

6 

3-02 

Not stated 

A 

Accumulators 




employed 

a; 

3-12 

Condensing 

B 

Accumulators 





employed 


3 25 

Not stated 

A 

Accumulators 





employed 


G'3 

Not stated 

A 

No aceumula- 

«*- 

c 'A 



tors employed 

03 sS 

8-2 

Condensing 

B 

Not stated 

C >* 





*—; « 

9-0 

Not stated 

A 

Accumulators 





employed 

CO 

CO u 

9-4 

Condensing 

B 

Not stated 

T~ O 

9-5 

Condensing 

B 

Not stated 

CC 

_ C3 

10-1 

Condensing 

B 

Accumulators 




employed 


11-9 

Not stated 

A 

Accumulators 

4-> 




employed 


12'5 

Not stated 

A 

Accumulators 





employed 


1S-1 

Condensing 

B 

Not stated 

sis 

23 0 

Condensing 

B 

Accumulators 

So® 




employed 


26-7 

Not stated 

A 

Accumulators 

^ ^ Pi 




employed 

a-* 0 C sc 

29-6 

Not stated 

A 

Accumulators 





employed 


41-5 

Not stated 

A 

Accumulators 

«E W 




employed 


45-0 

Both 

B 

Accumulators 





employed 


Table 


Annual Overall Efficiencies of Twenty- 


Kilowatt Hours delivered 

by Accumulators 

during Year. 

Kilowatt Hours by Accu¬ 

mulators in per cent, 
of Total Kilowatt Hours. 

Steam superheated or not. 

Average Amount of Super¬ 

heat in Degrees Cent. 

Quality of Coal used. 

177,600 

18-7 

Not stated 

Not stated 

German 

bituminous 

148,8S0 

15-4 

Not stated 

Not stated 

German 

bituminous 

Not stated 

Not stated 

Not stated 

Not stated 

Not stated 

Not stated 

Not stated 

Not stated 

Not stated 

Not stated 

200,300 

17-0 

Not stated 

Not stated 

Westphalian 

anthracite 

Not stated 

Not stated 

Superheated 

28° 

Small peas 

262,738 

12-7 

Not stated 

Not stated 

Westphalian 

bituminous 

Not stated 

Not stated 

Superheated 

Portion slightly 
superheated 

Best Welsh 
Derby pea nuts 

Not stated 

Not stated 

None 

Not stated 

Derby pea nuts 
Yorkshire 

211,000 

7-0 

Not stated 

Not stated 

steam 

Not stated 

Not stated 

Superheated 

Very little 
superheat 

Not stated 

Fife small 

180,000 

5 6 

Not stated 

Not stated 

Scotch anthracite 
and German 
anthracite 

Not stated 

Not stated 

Not stated 

Not stated 

German lignite 

Not stated 

Not stated 

Not stated 

Not stated 

Not stated 

Not stated 

Not stated 

Superheated 

Not stated 

German lignite 

Not stated 

Not stated 

Superheated 

Part superheated 
to 23S° 

Smudge 

Not stated 

Not stated 

None 

Not stated 

Slack 

Not stated 

Not stated 

Superheated 

28° to 56° 

Slack 

Not stated 

Not stated 

Not stated 

Not stated 

Lignite briquettes 
and gas coke 

Not stated 

Not stated 

Not stated 

Not stated 

Cardiff and 
Westphalian 

Not stated 

Not slated 

Not stated 

Not stated 

Not stated 

Not stated 

Not stated 

Superheated 

Superheated 
to 260° 

Washed nuts 

2,491,000 

9-4 

Not stated 

Not stated 

Westphalian 

bituminous 

275,000 

0-93 

Not. stated 

Not stated 

Cardiff 

1,188,000 

2-86 

Not stated 

Not stated 

German lignite 

Not stated 

Not stated 

Superheated 

Part superheated 
to 50° 

Washed slack 


We shall now put forward a table (XL.) of thermal efficiencies of power station 
plants which cover a wide range of load factors and size of generating units. 

In the preparation of this table we have not adopted any impossible ideal, but 
wish it to be understood that the figures given for efficiencies are within the range of 
possibilities, and have been attained in one or two instances. In the preparation of 
the table we have embodied all the principles set forth in this chapter, and the plants 
are taken as provided with superheaters, economisers, feed-water heaters, steam- 
driven auxiliaries, with boilers and condensers properly proportioned, and an ample 
supply of circulating water for the condensers and at a convenient level. 

It is not often that it is possible to obtain all the advantages in one plant. 

136 


Water 
























































THE ELECTRICAL POWER GENERATING PLANT 
XXXVIII. 


six Electrical Generating Stations. 


Calorific Value in Kilo¬ 
watt Hours per Ton. 

Number of Tons of Coal 
burned per Year. 

Price in Shillings per 

Ton. 

Use to which the Elec¬ 
trical Energy is put. 
Light, L. ; Traction, T. ; 
Power, P. 

Average Load Factor 
of Generating Station 

per Year. 

Date of End of Year for 

which Data applies. 

Year of Working. 

(O) 

Total Kilowatt Hours 

of Calorific Value of Coal 

burned per Year. 

(D) 

Total Output in Kilo¬ 

watt Hours during Year. 

100 D 

C 

Efficiency of Generating 

Station in per cent. 

8,600 

2,080 

21-4 

L P.T. 

18-8 

1904 

6th 

17,900,000 

948,000 

5-3 

8,500 

2,730 

9-6 

L.P.T. 

27-5 

1903—1904 

4th 

23,200,000 

965,000 

4-16 

0,000 

3,100 

11-0 

L.T. 

15-4 

March, 1904 

6tli 

27,900,000 

1,000,000 

3-58 

7,700 

4,250 

11-5 

L. 

16-0 

March 25, 1904 

7th 

32,700,000 

1,090,000 

3-34 

8,150 

3,458 

18-0 

L.P.T. 

14-05 

1903—1904 

5th 

28,200,000 

1,177,000 

4"2 

0,100 

8,200 

7*7 

T. 

13-8 

March, 1903 

10th 

74,500,000 

1,330,000 

1-79 

9,050 

4,190 

14-2 

L.P.T. 

43-6 

1903—1904 

5th 

37,900,000 

2,070,000 

5-5 

8,500 

17,300 

10-75 

T. 

11-6 

March 31, 1904 

6th 

147,000,000 

2,250,000 

1-52 

9,500 

11,300 

12-3 

L. 

121 

March 31, 1903 

10th 

107,300,000 

2,900,000 

2-7 

S,320 

5,040 

12*6 

L.P.T. 

20-5 

1903—1904 

12th 

49,400,000 

3,020,000 

6-1 

7,100 

10,800 

8-2 

T. 

17-4 

March 15, 1904 

Not stated 

76,600,000 

3,120,000 

406 

7,100 

7,500 

16-3 

L.P.T. 

13-7 

1903—1904 

14th 

53 , 200,000 

3,250,000 

6-1 

5,600 

22,580 

10-1 

L.P. 

35-0 

1904 

11th 

126,300,000 

6,260,000 

4-95 

8,020 

10,500 

9-75 

T. 

Not stated 

— 

Not stated 

132,500,000 

8,200,000 

6-2 

2,800 

44,000 

Not stated 

T. 

76-7 

1904 

9th 

126,000,000 

8,98S,000 

714 

7,060 

26,100 

5-0 

L.P. 

14-5 

March 25, 1905 

Not stated 

184,000,000 

9,400,000 

5-1 

7,700 

20,300 

8'2 

T. 

Not stated 

March 25, 1904 

11th 

156,500,000 

9,500,000 

6-05 

9,320 

18,000 

7*7 

L.P.T. 

28-6 

March 31, 1905 

Not stated 

168,000,000 

10,100,000 

6-10 

S,350 

20,S00 

13 0 

L.P.T. 

38-1 

1904 

13th 

173,500,000 

11,890,000 

6-85 

8,750 

19,800 

Not stated 

L.P.T. 

40*1 

1904 

10 th 

173,000 000 

12,4S0,000 

7-21 

0,300 

30,184 

16-45 

T. 

Not stated 

April, 1905 

Not stated 

290,000,000 

18,100,000 

6-45 

8,100 

35,270 

6*4 

T. 

30-8 

May 31, 1905 

5th 

286,000,000 

23,000,000 

8-06 

8,750 

40,800 

17-1 

L.P.T. 

34-3 

1903—1904 

16th 

357,000,000 

26,650,000 

7-46 

8,750 

43,800 

Not stated 

L.P.T. 

Not stated 

1904 

5th 

383,000,000 

29,600,000 

7-75 

7,750 

50,000 

Not stated 

L.P.T. 

35-2 

1904 

3rd 

433,000,000 

41,500,000 

9-61 

8,940 

75,000 

10-0 

L.P.T. 

1 

25-5 

March 31, 1905 

Not stated 

670,000,000 

45,000,000 

6-72 


for condensing is often not available, and cooling towers have to be used ; in other 
cases the financial conditions may be such that a cheaper and therefore less efficient 
plant is the economical one to adopt. In these cases, allowances can readily be made 
foi the special circumstances of the case. None of the stations described possess all 
the advantages, but when their disadvantages are allowed for, one, if not two, of the 
plants come very close to the attainable as thus defined. 

Provided all the conditions are similar, that is, provided that the size of unit in 
each case bears the same ratio to the average load, the efficiency of the station will 
depend on the size of the unit of generating plant. The basis of the table is therefore 
the efficiency of the engine and generator and its variation with size. The term engine 

G7 



















































































ELECTRIC RAILWAY ENGINEERING 


includes either reciprocating engine or turbine, and no limitations are imposed in 
the choice of type, hut it is assumed that the engine is the most efficient of its type, 
and is working at its most economical point, and at the most economical vacuum. 
The sizes we have selected range from 10,000 down to 500 kilowatts, and in Table XL. 
the efficiencies are the combined efficiencies of the engine and generator, and 
represent the best which have been yet attained. The steam pressure selected is 
165 lbs. per square inch, and superheat 300 degrees F. 


Table XL. 


Table of Thermal Efficiency of Engine and Generator and Overall Efficiency of 

Complete Plant on Steady Load. 


Economical Rating of 
Engine and Generator. 
(Kilowatts.) 

Nett Energy supplied 
to Engine per 
Kilowatt Hour Output 
(B.T.U.) 

Thermal Efficiency of 
Combined Set. 

Total Energy in Fuel 
burned per kilowatt 

H our Output. 
(B.T.U.) 

Overall Efficiency. 

10,000 

15,000 

0-229 

20,600 

0-167 

5,000 

15,320 

0-224 

21,100 

0-163 

2,500 

15,900 

0-216 

21,850 

0-157 

1,250 

16,820 

0-204 

23,100 

0-149 

1,000 

17,270 

0-199 

23,700 

0-145 

750 

17,970 

0-192 

24,510 

0-140 

500 

18,930 

0-181 

26,150 

0-131 


The figures given in the second column are nett amounts, and do not take into 
account the energy required for air and circulating pumps, or losses in condenser. 
After allowing for these, and for losses in radiation from piping, boiler, and economisers, 
and for the energy supplied to the chimney to produce a draught, we obtain the 
figures in the fourth column, being the total energy in the fuel. We have now the 
energy to be provided by the fuel per kilowatt hour under the best conditions and for 
steady load. In order to obtain the efficiencies of the power plant under service con¬ 
ditions, we take the above table as a basis. We have first to allow for a fluctuation in 
the load, where, although the output in a given time may be the same as for steady 
load, the load may have fluctuated between wide limits ; next, allowance has to be made 
for variation in the load, as a result of which the plant is working part of the time at 
a less efficient part of its range. The losses suffered depend upon the nature of the 
load curve, and in the following it is assumed that the minimum load can be supplied 
economically from the unit, and that the new load capacity is drawn upon before an 
additional unit is put in parallel. A further, and by far the greater, source of loss 
which follows from the variation in the load, is due to the necessity of keeping up the 
fires and boilers in readiness for the maximum load. The coal consumed may amount 
to as much as 6 lbs. per square foot of furnace per hour, the energy being dissipated 
by radiation from boilers, and piping, and engines, which must be kept in a state of 
readiness. All these losses are taken into account in Table XLI., the values being 
based on our general experience and specific tests and observations. The values are 
plotted in terms of the size of unit and the load factor. By load factor in this case is 
meant the “ daily ” load factor obtained from the daily load curve as distinct from the 

138 
















THE ELECTRICAL POWER GENERATING PLANT 

annual load factor, as it is upon this that the efficiency or otherwise of the workine 
depends. ° 


Table XLI. 


I able of Overall Efficiencies of Steam 


Plants under Service 


Conditions. 


Daily Load 
Factor, 
per cent. 

Economic Rating of Unit of Generating Plant in Power Station in Kilowatts. 

10,000 

1 

5,000 

2,500 

1,250 

1,000 

750 

500 


Thermal Efficiency of Plant, being Ratio of Output of Generating Plant to the Input into the Furnaces. 

100 

0-158 

0-155 

0-150 

0-141 

0-138 

0-133 

0126 

90 

0-151 

0-147 

0-142 

0-135 

0-132 

0-127 

0-118 

80 

0-144 

0-141 

0-135 

0-128 

0-125 

0-121 

0-113 

70 

0-136 

0-133 

0-128 

0121 

0-118 

0-115 

0-108 

60 

0-127 

0-124 

0-120 

0-113 

o-iio 

0-106 

0-101 

50 

0-116 

0-114 

0-110 

0-104 

0-102 

0-098 

0-093 

40 

0-104 

o-ioi 

0-098 

0-093 

0-090 

0-087 

0-082 

30 

0-089 

0-087 

0-084 

0-079 

0-078 

0-075 

0-071 

20 

0-071 

0-067 

0-065 

0-061 

0-060 

0-057 

0-054 

10 

0-043 

0-041 

0-039 

0-036 

0-035 

0 034 

0-032 


The values given are such as the station engineer should obtain provided he 
has all the advantages assumed. If any specific advantage, such, for instance, as 
superheat, is absent, or if he is placed so that the water supply for condensing purposes 
is limited, or if the water has to be lifted a considerable height, the value of such 
deficiency can be readily calculated, and, after applying the correction to the values 
given in the table corresponding to the load factor and size of unit, the result can 
then be applied to gauge the actual performance of the plant. 


139 







































Chapter VI 

THE HIGH TENSION TRANSMISSION SYSTEM 

I N the last chapter we traced the energy from the fuel up to the outgoing mains 
from the generating station. Up to that point neither the capital costs nor the 
generating costs are appreciably different whether continuous-current or alternating- 
current energy is supplied, nor will the voltage of the supply affect the result to any 
considerable extent. 

But we now come to a link in the system where the cost is a function of the 
form of electrical energy and of the voltage at which it is supplied. In the most 
extensive and approved modern plants, the electrical energy is delivered from the 
generating station in the form of three-phase high tension currents, and is trans¬ 
mitted in this form to sub-stations, where by means of suitable converting plant, it 
is transformed into continuous current. This continuous current is supplied to the 
conducting rails, or to the overhead trolley line, and thence to the motors on the cars 
or trains. Where the area over which the energy is to be transmitted is not extensive, 
it may often he preferable to supply continuous current direct from the generating 
station and thus avoid the necessity for sub-stations. There are also a few plants 
where high tension continuous current is supplied from the generating station. 
During the last couple of years, a great deal of attention and study has also been 
given to single-phase systems of traction, which permit of transmitting at high tension 
direct to the car or train, on which is carried an equipment of transforming devices 
and alternating-current commutator motors. In a related system, the train receives 
high tension alternating current, which is transformed by means of a motor-generator 
carried on the train, into low tension continuous-current, and is distributed in this 
form to the motors. Polyphase motors are used on the car or train on quite a 
number of roads, and for certain cases this system is excellent. 

We shall work out the general case of electric traction on the basis of the first of 
the above-named systems, since this system has come into very extensive and 
successful use, and, so far as it is displaced by one or other of the alternative 
systems, this displacement will occur very gradually, so that for several years, at 
any rate, a large amount of work will be done by the three-phase continuous-current 
system. 

In cities, and wherever the local conditions or regulations require it, the three- 
phase high tension transmission system is installed with underground cables. A 
pressure of 11,000 volts between cores has so frequently been employed that w r e may, 
for our present purpose, take it as standard. A higher voltage would, at the present 
state of development in cable manufacture, rarely be economical, since, as we shall 
see, even at 11,000 volts, the cost, including installation, is from three to twenty 

140 


THE HIGH TENSION TRANSMISSION SYSTEM 

times the cost of the contained copper according to the cross-section per core. This 
multiplier rises rapidly with the voltage. In special cases a lower voltage is more 
economical, but for all extensive systems we may take 11,000 volts as the basis, at 
any rate for preliminary estimates. As the neutral points of the armature winding 
of the high tension generators are grounded at the generating stations, the pressure 

florn any core to earth is — ’ = 6,350 volts. 

V 3 

Estimation of the Cost of High Tension Cables. 

. The data glven cable manufacturers in their catalogues, while often very exten¬ 
sive, are rarely m the form most useful to the engineer in designing projects. He must 
of course, before the project is completed, have recourse to precise estimates from the 
cable manufacturers, but prior to that stage he is more especially concerned with the 
relative costs of complete cables for different voltages. These are, for his purpose, most 
conveniently expressed m terms of the weight of the copper in the cable, or, more 
precisely, it is convenient for him to figure on a cost in pounds sterling per metric ton 
qt contained copper. These data,‘together with some details of construction, guarantees 
etc suffices for obtaining a rough estimate of the percentage of the total cost which 
wil be reqmred for the cables. This is all that is required up to the later stages 
of the designing of an installation. This small amount of data he should, however, 
have at hand in as compact a form as practicable. 

The following brief descriptive specification may be taken as representative of the 
most generally employed three-phase cables. 

Specification .—Three cores of stranded copper conductors, symmetrically disposed 
with relation to one another, and individually insulated with paper, or other insula¬ 
tion, are spirally assembled together, the pitch of the spiral varying chiefly as a 
function of the diameter per core. The three cores thus assembled together, are 
covered with paper or other insulation of suitable thickness. 1 An external coverirm 0 f 
ead is then applied, and this in turn is often protected by an armouring, frequently 
consisting of two layers of steel tape. 1 Sometimes the steel or iron covering is, in its 
turn, protected by a final covering of tough jute or other suitable material. 

Such a cable, when for 11,000 volts, is generally guaranteed to withstand for 
1 hour, the application of an effective alternating current voltage of three times the 
normal voltage when tested at the manufacturer’s works, and a further test, with at 
least double the normal voltage, when finally installed. This test is made between 
each pair of cores, and from each core to lead. 

Recently there has appeared a new type of cable insulated with varnished 
cambric. The construction of the cable is as follows :—Specially prepared cotton 
fabric is coated on both sides with multiple films of insulating varnish. The coated 
cloth, cut into strips, is applied to the copper core with films of special non-drying 
viscous and adhesive compound between the copper and the taping. 

The result is a flexible and homogeneous insulating wall of great dielectric 
strength. This insulation, unlike paper, does not absorb moisture, and it is therefore 
unnecessary to seal the ends. It is stated that leaded varnished-cambric cable 
installed in 1898 on 11,000 volts circuits in connection with overhead transmission 
lines, exposed to lightning discharge, is still in use without failure or deterioration. 

1 The Engineering Standards Committee’s specifications for thicknesses of dielectric and lead 
sheathing and armouring are given on pp. 162 to 164. 

141 



ELECTRIC RAILWAY ENGINEERING 


The prices of cable vary chiefly with the normal voltage and with the cross 
section per core. A further but less important variation in price is introduced by 
the particular specification as regards the application of armouring or other covering 
over the lead. The chief components of the cost are, however, represented by the 
copper, the insulation, the lead, and the installation of the cable. This last item, 
the installation, tends to partly offset variations with respect to whether armouring 
and further outer coverings are or are not used. For an armoured cable will 
require less expensive further provisions than in the case of a bare lead cable. 
Of course the cost of installing varies greatly. The prices which will be given in 
subsequent tables may be taken as applying to cables installed in the tunnels of 
underground electric railways, and in other cases in subways especially provided for 
the reception of cables, and will not cover any part of the cost of construction of such 
subways, or of the cost of opening up the streets when other locations are 
necessary. 

"With these premises we may take the prices given in Table XLII. as repre¬ 
sentative, though in cases where competition is exceedingly keen, the price for 
large quantities may be as much as 20 per cent, lower. Such variations will 
in no way invalidate the general engineering problem as set forth in this chapter. 

The cost of copper on which Table XLII. is based, is taken at £100 per ton. 
This is the cost of the copper core as stranded, including charges due to wire 
drawing and stranding. O’Gorman in a paper entitled “ Insulation on Cables,” 1 
allocates this £100 as follows :— 

“ G.M.B. copper in the market, £77 ; cost of wire drawing, £8 ; stranding, £5 ; 
shop charges and administration, £10 per ton.” 

The current market price for copper is a few pounds lower than £77, so that 
£100 per ton for the copper cores is rather high. This, however, will cover 
market fluctuations, and moreover, if more accurate estimates are desired, it is 
easy to convert costs which are based on a decimal figure, as £100. The results 
set forth in Table XLII. have been plotted in Figs. 122 and 128, the former 
giving the cost of complete cable in pounds per ton of copper contained in 
the three cores, and the latter showing the ratio of the cost of complete cable 
to the cost of contained copper at £100 per ton for various voltages and cross 
sections of core. 

In the paper by O’Gorman referred to above, the following data as to the 
cost of insulation and lead sheathing are given :— 

“ Copper is taken at £100 a ton (or lid. per pound), a price which is rather 
too high. This is to cover market fluctuations. I justify its use because the 
deductions and curves which follow are only comparative, and the effect on the 
total price of the various insulation thicknesses outweighs the price of copper on 
both small and large sizes. For example, between 15,000 kilowatts and 80,000 
kilowatts the price of cable is nearly constant, although the copper varies from 
053 sq. ins. to 1*5 sq. ins. Another reason for taking a high price 
for copper is that the labour of handling and jointing will depend on the 
weight of the cable even though the radial thickness of insulation may go down. 
Lastly, the decimal figure £100 is easy to correct if a more accurate estimate is 
available. 

“ Insulation is taken at £50 per ton. This price is too low for rubber cables, 


1 “ Journal of the Institution of Electrical Engineers,” Yol. XXX., p. 608 (March 7th, 1901). 

142 


Table XLII. Data of Cables fob Various Voltages, 


Particulars of Copper Conductor. 


500 R.M.8. Volts between Cores. 


o 

£ 

s 

9 

c 

C 

o 

s 

o 

£2 

P 

i 

X 

■A 

l 

the Cable.i 

Diameter over each Stranded 
Core. 

a 

2 d 

h 

— 

« ® 

S s 

c — 

5 2 

x C 
"v. •~~ 

9 C 
« 

Normal Current per Core at 
1,000 Amps, per Square Inch. 

Weight of contained Copper 

in the three Cores, in Tons 

per Mile. 

Cost of the Copper contained 

in the three Cores of the Cable. 

Copper at £*100 per Ton.2 

Diameter of Complete Cable. 

Weight of Complete Cable in 

Tons per Mile. 

Square 

Milli ¬ 

metres. 

Square 

Inches. 

Milli¬ 

metres. 

Mils. 

Ohms 

per 

Mile. 

Amps. 

Tona8 

ner 

Milo. 

Pounds 

per 

Mile. 

Milli¬ 

metres. 

Inches. 

Tons 

l>cr 

Mile. 

4-84 

0-0075 

2-80 

110 

5-61 

7-5 

0-207 

20-6 




9-68 

0-015 

4-00 

158 

2-81 

150 

0-415 

41-5 




10-0 

00155 

4-10 

168 

2-705 

15-5 

0-428 

42-8 

32 

1-26 

5-23 

14-2 

0 022 

4-95 

195 

1-92 

22-0 

0-617 

61-6 




160 

0-0248 

5-35 

210 

1-69 

24-8 

0-685 

68-4 

34 

1-34 

5-96 

19-4 

0-030 

5-80 

280 

1-40 

300 

0-826 

82-8 




23-9 

0-037 

6-40 

250 

1-26 

37 0 

1-02 

102-0 




25-0 

0-0387 

6-50 

260 

1097 

38-7 

1-07 

107-0 

38 

1-497 

7-56 

29-1 

0-045 

7-10 

280 

0-957 

45-0 

1-24 

1240 




33-5 

0-052 

7-60 

300 

0-81 

52-0 

1-435 

142-5 




860 

0-0542 

7-75 

310 

0-772 

54-2 

1-525 

152-3 

41 

1-615 

8-70 

38-8 

0-060 

8-15 

320 

0-702 

600 

1-655 

165-0 




43-2 

0-067 

8-60 

340 

0-629 

67-0 

1-850 

185-0 




48-4 

0-075 

9-10 

360 

0-561 

75-0 

2-07 

206-5 




50-0 

0-0775 

9-20 

360 

0-540 

77-5 

2-14 

213-0 

44 

1-732 

10-30 

580 

0-090 

100 

390 

0-469 

900 

2-48 

248-0 




67-6 

0-105 

10-6 

420 

0-400 

105-0 

2-90 

289-0 




70-0 

0-1085 

10-9 

430 

0-386 

108-5 

2-99 

298-0 

49 

1-930 

13-37 

77-6 

0-120 

11-8 

450 

0-350 

1200 

3-31 

330-0 




87-5 

0-136 

12-5 

490 

0-312 

136-0 

3-75 

364-0 




95-0 

0-1473 

12-7 

500 

0-285 

1470 

4-06 

405-0 

53 

2-085 

16-10 

96-8 

0-150 

12-8 

500 

0 - 2 H 1 

150-0 

4-14 

414-0 




106-7 

0-166 

13-2 

520 

0-255 

166-0 

4-58 

458-0 




1160 

0-180 

14-0 

550 

0-235 

180-0 

4-93 

493-0 




120-0 

0-186 

14-3 

560 

0-225 

186-0 

5-14 

515-0 

58 

2-285 

19-65 

125-5 

0-195 

14-6 

580 

0-218 

195-0 

5-54 

533-0 




135-2 

0-210 

15-1 

600 

0-200 

2100 

5-75 

575-0 




144-9 

0-225 

15-6 

620 

0-187 

225-0 

6-16 

615-0 




150-0 

0-2325 

16-0 

630 

0-180 

232-0 

6-44 

642-0 

63 

2-480 

23-80 

155-4 

0-241 

16-2 

640 

0-174 

2410 

6-60 

660-0 




165-2 

0-256 

16-7 

660 0-163 

256-0 

700 

700-0 




175-0 

0-272 

17-2 

680 0-155 

2720 

7-45 

745-0 




184-8 

0-286 

17-7 

700 

0-147 

286-5 

7-85 

784-0 

68 

2-680 

28-70 

185-0 

0-287 

17-8 

700 

0-145 

287-0 

7-91 

790-0 




193-8 

0-301 

18-1 

710 

0-140 

3010 

8-22 

821-0 




210-0 

0-3255 

21-0 

830 

0129 

325 0 

8-98 

897-0 

72 

i 

2-840 

31-70 


■ 3 1 


£ a 


U 5 
©£ 


£ ° * 
e £ & 

< 5 §° 


Pounds 
per Pounds. 
Mile 


12-2 

8-76 

7-06 

5-78 

4-80 

4-43 

3-98 


138 

164 

222 

270 

342 

466 

576 


321 

240 

207 

177 

160 

102 

142 


3-82 704 137 


3-69 874 135 


3-63 

3-51 


1,057 133 

1,191 132 


3-2 

2-4 

2-1 

1-77 

1-60 

1-52 

1-42 

1-37 

1-35 

1-33 

1-32 


ai| 

°|s 

1st 

§£> i 

S* =o 
o:->g 


Kilo¬ 

watts. 


13-4 

21-5 

33-5 

470 

67-0 

937 

128-0 

1610 

201 0 

248-0 

281-0 


1,000 B.M.S. Volts between Cores. 


Milli¬ 

metres. 


Inches. 


35 1-38 

87 I 1-46 

41 1-615 


43 


48 


52 


56 


1-695 


1-89 


2-05 


221 


61 2-405 21-10 


.2 S 

§£• 
O ® 

og 


Tons 

per 

Mile. 


0-11 

6-92 

8 - 53 

9 - 34 

12-56 

14-32 

18-04 


5 * 

25 


14-25 

10-10 

7-97 

6-12 

5-86 

4-79 

4-44 

410 


h 

I! 


Pounds 

Mila. 


166 

198-5 

253 

297 

406 

603 

644 

780 


65 2-56 23-65 3-671918 


ai 

~s 


o J 


© s 
o 5 
©. 


Bound* 

388 

287 

239 

195 

190 

168 

158 

152 

142 


-© .1 
o c. 


3,000 R.M.8. Volts between Cores. 


0) _ 
©I £ 

>. r ? S 

•i — Z 

a s* 

Eli- 

%£< 

|S§ 

2 


3-88 

2-87 

2-39 

1-95 

1-90 

1-68 

1-58 

1-52 

1-42 


Kilo¬ 

watts. 


26-8 
43 0 

67 0 

94 0 

134 0 

187-5 

254 0 

3220 

4020 


S 

9 

i 


Milli¬ 

metres. 


40 

42 

46 

50 

55 

60 

63 

67 


Inches. 


1-575 

1-655 

1-810 

1 - 970 

2 - 17 

2-365 

2-48 


C 9 

5 ~ 

?s 

U > 


Tons 

per 

Mile. 


as. 

w a. 

25 


7 - 4 

8 - 2 

9-72 

12-55 

15-92 

18-60 

20-90 


2-64 23-65 


Panada 
pet Pounds. 
Mile. 


17-25 

11-95 

9-08 

8-22 

7-44 

619 

5 T 5 

4-60 


§1 




$1 

°<£ 


217 

253 

822 

422 

543 

670 

805 

950 


506 

370 

301 

277 

254 

224 

198 

185 


o 

2 

3 . 
o * 


5 2 = 

©I £ 
S-i s 
Ig# 
Eli 

8S8 


7,000 R.M.S. Volts between Cores. 


6 06 
3-70 

301 

2-77 

2-54 

2-24 

1-98 


Kilo¬ 

watts. 


80-5 

129-0 

201-0 

282-0 

402-0 

562-5 

762 0 


1-85 966 0 


10,000 lt.M.S. Volts between Cores. 


15,000 R.M.8. Volts between Cores. 


ft 

2 

* 

1 

L 

*c 

I 

< 

i 


Weight of Complete Cable in 

Tons per Mile. 

Ratio of Weight of Cable to 

Weight of Copper. 

Cost of Complete Cable in 

Pounds per Mile. 

Cost of Complete Cable in 

Pounds per Ton of contained 1 

Copper. 

j Ratio of Cost of Cable to Cost 

of Copper. 

1 

# 

3 c — 

ass 

©I £ 

i|t 
*£ | 
g-s 

JS § 

5 

Kilo¬ 

watts. 

Diameter of Complete Cable. 

Weight of Complete Cable in 

Tons per Mile. 

Ratio of Weight of Cable to 

Weight of Copper. 

Cost of Complete Cable in 

Pounds per Mile. 

Cost of Complete Cable in 

Pounds per Ton of contained 

Copper. 

Ratio of Cost of Cable to Cost 

of Copper. 

Kilowatt Capacity of Cable 

at Unity Power Factor ana 

1,000 Amps. Square Inch. 

Milli¬ 

metres. 

Inches. 

Tons 

per 

Mile. 


Pounds 

Tier 

Mile. 

Pounds. 

Milli¬ 

metres. 

Inches. 

Tons 

per 

Mile. 


Pounds 

I>er 

Mile. 

Pounds. 


Kilo¬ 

watts. 

37-6 

1-48 

8-8 

42-6 

310 

1,500 

15-0 

90-8 

47-6 

1-87 

10-9 

52-6 

450 

2,170 

21-70 

130 

40-5 

1-60 

10-4 

25-0 

457 

1,100 

110 

181-6 

50-2 

1-96 

11-8 

28-4 

510 

1,230 

12-3 

260 

43-6 

1-72 

120 

19-3 

505 

610 

6-10 

363 

541 

2-13 

14 1 

171 

628 

760 

7-60 

520 

46-7 

1-84 

13-6 

11-0 

600 

485 

4-85 

545 

57-2 

2-26 

16-2 

131 

740 

596 

5-96 

780 

49-7 

1-94 

15-2 

9-2 

656 

397 

3-97 

727 

59-8 

2-855 

18 1 

10-9 

855 

516 

5-16 

1,040 

52-7 

2-08 

16-8 

8-1 

798 

386 

3-86 

908 

62-5 

2-46 

201 

9-7 

960 

464 

4-64 

1,300 

55-8 

2-23 

18-35 

7-4 

895 

361 

3-61 

1,090 

65-2 

2-57 

221 

8-9 

1,055 

425 

4-25 

1,560 

589 

2-32 

20 00 

6-9 

1,000 

345 

3-45 

1,270 

67-2 

2-645 

23-8 

8-2 

1,155 

398 

3-98 

1,820 

62-9 

2-48 

21-6 

6-5 

1,100 

832 

3-32 

1,454 

68-4 

2-69 

25-8 

7-8 

1,265 

382 

8-82 

2,080 

67 0 

2-64 

23-2 

6-2 

1,200 

320 

3-20 

1,647 

71-8 

2-825 

27-5 

7-34 

1,370 

365 

3-65 

2,360 

700 

2-76 

24-8 

60 

1,290 

313 

3-13 

1,815 

73-7 

2-90 

291 

7-03 

1,465 

354 

3-54 

2,600 

71-5 

8-82 

261 

5-7 

1,380 

302 

3-02 

2,010 

75-6 

2-98 

30-8 

6-72 

1,575 

344 

8-44 

2,870 

73 0 

2-87 

27-4 

5-55 

1,465 

296 

2-96 

2,180 

77-0 

3-03 

32-2 

6-53 

1,675 

340 

3-40 

8,120 

74-5 

2-93 

28-8 

5-40 

1,560 

290 

2-90 

2,360 

78-4 

3-085 

33-5 

6-28 

1,775 

332 

3-32 

8,380 

76-1 

300 

30-2 

5-27 

1,635 

284 

2-84 

2,540 

79-8 

3-14 

34-8 

605 

1,880 

327 

3-27 

3,640 

77-6 

306 

31-6 

5-15 

1,715 

278 

2-78 

2,720 









791 

312 

32-8 

4-97 

1,795 

272 

2-72 

2,920 









80-6 

317 

34-3 

4-90 

1,880 

269 

2-69 

3,100 









82-2 

3-22 

35-4 

4-75 

1,970 

265 

2-65 

8,350 









83-6 

3-29 

37 0 

4-70 

2,050 

261 

2-61 

3,530 









85-2 

3-35 

38-3 

4-67 

2,140 

260 

2-60 

3,640 










- | 
6 


69-5 

710 

72-5 

740 

75-6 

771 

78-6 

80-1 

81-6 

83-2 


Inches. 


2-74 

2-795 

2-855 

2-91 

2 - 98 

3 - 035 
8-095 

3-155 

3-21 

3-28 


u 

f* 

©:- 


Toils 

I»er 

Mile . 


18 - 23 

19 - 8 

21-4 

23 - 2 

24 - 6 

26-2 

27-8 

29-4 

311 

32-1 


a& 

55 

Tt o 


88-0 

47-7 

34-7 

280 

241 

20-3 

19-4 

17-8 

16-8 

15-45 


s: 

is. 

§1 
5 I 


Pounds 

per 

Mile. 


659 

727 

800 

860 

927 

994 

1,057 

1,130 

1,180 

1,260 


3 S 
o 8 
- S*o 
1 = 8 . 
- © ©- 
its 

o » 

♦a*© 
f. ~ 

O 3 

V o 


Pounds, 


3,180 

1,750 

1,300 

1,040 

910 

800 

737 

683 

638 

609 


Ss. 


31-8 

17-5 

13-0 

10-4 

9-10 

8-00 

7-37 

6-83 

6-38 

6-09 


Kilo¬ 

watts. 


195 

390 

570 

780 

962 

1,170 

1,350 

1,560 

1,740 

1,950 


20,000 R.M.8. Volts between Cores. 


O 

2 

J 2 

S 

9 

O 

o 

u 

s 

a > 

£ 

eS 

5 


Milli¬ 

metres. 


72-0 

740 

76 T 

78-1 

801 

82-2 

84-2 

86-3 

88-3 

90-3 


Inches. 


2-83 

2-91 

2 - 95 

3 - 07 
3-155 

3-235 

3-317 

3-39 

3-455 

3-555 


per 

Mile. 


23-5 

250 

26 - 4 

27 - 9 

29 - 3 

30 - 8 
321 

33-6 

351 

36-4 


5 " 

il- 

if 

£§ 

oi. 


a 1 

si 

38 

Pi 

£-.© g . 
Sr- © 
>- u 
£ 8 . 

O M 

c © 

■r. — 

O O 

O o 
08 


Pounds 

per 

Mile. 


11 . 3-5 

60-5 

43-0 

38-7 

28-7 

24-8 

22-4 

20-2 

19-0 

17-6 


800 

870 

940 

1,010 

1,080 

1,150 

1,210 

1,290 

1,350 

1,430 


Pounds, 


3,870 

2,100 

1,525 

1,210 

1,060 

930 

845 

750 

730 

685 


O 

o 

2 

$ & 

A 

28 

•/). 

6 ° 

O 

o 


3 El 
‘©Is 

♦J 3 

’o >- 5T 

as® 

3£S- 

5 a © 
o^S 


Kilo¬ 

watts. 


38-7 
21 0 

15-25 

12-10 

10-60 

9-30 

8-45 

7-50 

7-30 

6-85 


260 

520 

762 

1,040 

1,280 

1,560 

1,800 

2,080 

2,320 

2,600 


1 The cross-section of one core is equal to the sum of the cross-sections of all the component strands. 

2 Copper is taken at .£100 per ton of stranded conductor. See note on p. 142. 

8 liy “ ton ” is denoted the metric ton of 1,000 kilogrammes or 2,200 lbs. 
















































































































































































































































































. 





. 




























THE HIGH TENSION TRANSMISSION SYSTEM 

but as it is well known that the cost of fibre, together with its lead, is of the 
same order as rubber, it will follow that the general trend of the curves holds 
tor rubber also, only the maxima and minima will be more marked for any class 
of insulation dearer than I have selected unless the disruptive strength is 

correspondingly greater. Paper, P35 per ton ; impregnating oil, P7 ; labour, P10 • 
administration, etc., P'19. 

“ Lead was taken at P25 a ton to allow for the labour of lead covering, which 
is high. A thickness of 0T25 ins. was taken in all cases. This thickness is 
rather small for large cables, which sometimes take 0’15 or 0-18 ins. If this 
increase of lead had been allowed for, the rate at which the cost of cable 


Cross Section 



Fig. 122. Costs of High-Tension Three-Core Cables. 


increases with increase of output would have been still further diminished within 
practical limits of copper section, but the character of the curves 1 would not be 

altered, only accentuated. Best Spanish lead, PI5 per ton; labour, P3; administration 
P6 a ton.” 

The results of Table XLII. and of the curves of Fig. 123 bring out very clearly 
the fact that the cost of copper in cables, when for high tension work, is but a very 
small percentage of the total cost of the cables. 

On the basis of these data the curves in Fig. 124 have been prepared. 
These curves show that, while in regions like the western districts of America, 

1 The curves referred to are those published in the paper from which this extract is mad- 
They are for H.T. cables built up on O’Gorman’s principle of grading the dielectric, and are of 
a similar nature to the curves given in Fig. 124. 

M3 





































































































































ELECTRIC RAILWAY ENGINEERING 


it is of distinct advantage to use extremely high potentials for overhead lines 
with bare conductors, much lower pressures will give the most economical results 



Fig. 123. Curves showing the Ratio of the Cost of Three-Core Cables complete, to the 
Cost of Copper contained in the Three Cores for oOO to 20,000 Volts between Cores. 

where the regulations of the authorities require the use of underground cables. 
The curves show the most economical voltage for every case, when considered from 
the standpoint of the cost of the transmission cables alone. But since the cost 

144 







































































































































Fig. 124. Costs of Cables for Transmission Lines, for transmitting 1,000 to 16,000 k.w. to a Distance 

of 10 to 40 Kilometres at Power Factors of DO and 0-8. 




























































































































































































































































































































































































































































































































































































































































































































































THE HIGH TENSION TRANSMISSION SYSTEM 

of the cables, as revealed by these curves, generally increases but slowly as the 

18 low “ ed > ‘ he ‘““eased cost by the use of a considerably lower voltage 
often be oftset by the slightly lower cost of the generating and transforming 

::Sd intr xs. to “°™’ owing to ^ 

any rest ve'^th 1 ' 8718 t ? ns “ ltt ? d , by a siu « le three -eore cable, which would not leave 
“ n f 1 ’ e , ca8e , of a breakdown, and also results for the case of two three-core 

cables being used, half the energy being transmitted over each cable. This latter is the 
moie usual case m spite of the greater cost; in fact, the use of a single cable would 
afloid altogether insufficient reliability. With the exception of the groups of curves 
E and I all the other groups of curves in Fig. 124 are based on the employment of two 

case P ' 3nd ® nUhlee - core aablas ; each carrying normally one-lialf the total energy. In the 
case of the temporary breakdown of one of these cables, it is generally customary to 

unH the°l' el ° a< 1 1 1 ° her cabIe ’ a " d t0 8 et alon 8 with as small a load as practicable 
nil l e damaged cable is repaired. Of course, in very important installations, more than 

two independent cables are used, two sufficing to carry the normal load continuously 
1 he curves are self-explanatory. Ten per cent, line loss has been employed in the 
calculations ; but fairly accurate results for other values of line loss can be deduced 
from the curves without much extra calculation. Where sub-stations employing rotary 
converters are supplied over the high tension cables, five per cent, line loss, or even 
Jess, is desirable, otherwise the regulation will be very unsatisfactory. 

In the curves of Fig. 124, it will be noted that at a certain voltage in each 
case, the cost of the cables reaches a minimum value. At voltages higher than this, 
the cost of the insulation preponderates, and at lower voltages the cost of the cornier 
rendering the complete cable more expensive at pressures higher or lower than that 
foi minimum cost. The voltage at which minimum cost occurs, is higher the greater 
lie power transmitted, or the greater the distance to which it is transmitted, and the 
ower the power factor. It is also higher in the case of a single cable transmitting 
the whole of the power than for two cables each carrying half the power. 

In Figs. 125, 126, 127, and 128, the minimum cost of cables has been plotted 
as a function of the power transmitted. Figs. 125 and 126 are both for unity 
powei factor, but using one cable in Fig. 125 and two cables in Fig. 126. Figs. 127 

anc 128 are both for a power factor of 0’8, and using one cable in Fig. 127 and two 
cables in Fig. 128. 

ffi -9 T S !“™ ° T UrveS for distances of 10, 20, 80, and 40 kilometres 

(6 2 1- 4, 18 6, and 24-8 miles). In all these curves the cost which occurs at the 

“° 8 ‘ eC ? n °“ 1Cal V0ltage h f been employed, this voltage ranging from 9,000 to 
18,000 in the cases considered, as will be seen from Fig. 124 These curves 

bring out very clearly the fact that the cost of cables for transmitting power at high 
pressures is by no means proportional to, although it increases with, the power trans- 
mitted and the distance of transmission. This is because the cost of the copper 
constitutes only a comparatively small proportion of the total cost, the insulation cost 
emg sev ei'al times that of the copper. This has already been pointed out in 
connection with Table XLII. and in the curves of Fig. 123, where the ratio of cost 
of complete cable to cost of contained copper has been tabulated and plotted. 

. Ir J Table XLIL fche cross sections of the conductors may appear to be very 
miscellaneous and without much consecutive uniformity. This is due to the fact that 

E.R.E. I45 



Fig. 127. Fig. 128. 

Figs. 125, 126, 127, and 128. Curves showing Minimum Costs of Cables for transmitting 
1,000 to 8,000 k.w. to a Distance of 10 to 40 Kilometres. See Fig. 124. 

































































































































































































































THE HIGH TENSION TRANSMISSION SYSTEM 

the. data necessary for the compilation of this table, were deduced from the lists of 
various British and Continental manufacturers, whose cross sections usually conform 
o some number of. strands of certain wire gauges which do not give even figures 
or other uniformity in their cross sections. 


It would be possible with the data already arranged in Table XLII. to compile 
another similar table with a corresponding set of data, but for cross sections of cable 
coies increasing regularly and by some fixed increment, for instance, starting with a 
minimum cross section of, say, 25 sq. mm., and increasing this by 25 sq. mm. each 
time, or a similar even section and increment in square inches. Such a table would 
be desirable, but as its preparation would involve a large amount of detail work, we 
have not time to prepare it for the present volume. While mentioning this matter 
of conductor cross sections, we would draw attention to the Engineering Standards 
Committee s recommendations. In their report No. 7, designated “ British Standard 
Tables of Copper Conductors and Thicknesses of Dielectric,” they give a table for 
laige sizes of stranded conductors for electric supply, in which the smallest cross, 
section is 0 025 s.q. in., increasing by regular increments of 0025 sq. in. in the 
smallei of these sizes, 0’05 sq. in. in the intermediate sizes, and 0 - l sq. in. in the 
laigest sizes. This gives a scale of cross sections of some even number of thousandths 
of a squaie inch, increasing by a fixed number of thousandths of a square inch. 

Table XLIII. is from the above-mentioned report:— 


Table XLIII. 

British Standard Sizes of Stranded Conductors for Electric Supply. 


Approximate 
Weight per 
Statute Mile 
in 100 Lbs. 

Area of 
Conductors in 
Square Inches. 

Number and 
Diameter 
in Inches of 
Strands. 

5 

0-025 

7/-068 

10 

0-050 

7/-095 

10 

0-050 

19/-058 

16 

0-075 

19/-072 

21 

o-ioo 

19/-082 

26 

0-125 

19/-092 

32 

0-150 

19/101 

31 

0-150 

37/-072 

41 

0-200 

37/-082 

51 

0-250 

37/-092 

61 

0-300 

37/-101 

73 

0-350 

37/-110 

84 

0-400 

37/-118 

84 

0-400 

61/-092 

95 

0-450 

61/-098 

101 

0-500 

61/-101 

116 

0-550 

61/-108 

121 

0-600 

61/-110 

138 

0-650 

61/118 

142 

0-700 

91/-098 

151 

0-750 

91/-101 

160 

0-800 

91/-104 

179 

0-900 

91/-110 

207 

1-000 

91/-118 

211 

1-000 

127/-101 


For cables designated “intermediate sizes ” (of cross sections from 0 025 to 0*25 
sq. in.), and for those designated “small sizes” (cross sections up to 0025 sq. in.), 
the Engineering Standards Committee have adhered to three, seven, nineteen, or 

147 L 2 















ELECTRIC RAILWAY ENGINEERING 


thirty-seven strands of some S.W.G. wire, increasing the number of strands with 
the cross section. 

Temperature Fuse in Cables. 

The permissible current density and consequent temperature rise of the cable is 
affected by the method of laying and armouring. 

The surroundings of the cable, as regards whether it is laid in conduits or on 
brackets, with its exterior free to the circulation of the air, also affect its heat- 
radiating properties, and thus also the permissible current density. 

There is a great scarcity of published information regarding the heating of cables 
under working conditions. The problem must be affected largely by the method of 
laying the cable, whether in air on racks, or in conduits in the earth; in the latter 
case, the depth below the surface of the earth, and the nature and conductivity of the 
soil, will also have a hearing on the heating. Some results by L. A. Ferguson 1 on a 
few particular cables are given later on, but there is a wide field open for investigation 
as to how the heating of cables is affected by each of the considerations enumerated 
above for different classes of cable of various sizes and voltages. Before any standard 
current densities were recommended, it was general practice to allow a current density 
of about 1,000 amperes per square inch, regardless of the type of cable and method 
of laying. Tables XLIY. and XLV. give the maximum current densities allowable for 
copper wires employed in cables, as defined by the Buies of the Institution of Electrical 
Engineers (Great Britain), and by the German Society of Electricians (the latter are 
stated for voltages above 1,000 volts). 

Table XLIY. 

Maximum Permissible Current in Copper Conductors according to the Pules of 


the Institution of Electrical Engineers. 


Size S.W.G. 

Section in 
Square Inches. 

Permissible Current 
for Situations 
where the External 
Temperature is 
above 100° F. 

Corresponding 

Current 

Density. 

| Permissible Current 
where External 
Temperature is 
considerably lower 
than 100° F. 

Corresponding 

Current 

Density. 

18 or 62/38 or 97/40 . 

•00181 

3-1 

1710 

4-2 

2320 

3/22 . 

•00185 

3-3 

1780 

4-4 

2380 

17 or 130/40 . 

•00246 

4-0 

1625 

5-4 

2200 

3/20 . 

•00306 

4-8 

1570 

6-6 

2160 

16 or 110/38 or 172/40 . 

•00323 

4-9 

1515 

6-8 

2100 

15 .... 

•00409 

5-9 

1440 

8-2 

2000 

7/22 . 

•00431 

6-2 

1430 

8-7 

2020 

14 or 172/38 or 7/214 . 

•00502 

7-0 

1390 

9-8 

1950 

3/18 . 

•00544 

7*5 

1380 

11-0 

2020 

7/20 . 

•00715 

9-3 

1300 

13-0 

1820 

7/18 . 

•01270 

14-0 

1100 

21-0 

1650 

19/20 . 

•01940 

20-0 

1030 

30-0 

1550 

7/16 . 

•02260 

23-0 

1020 

34-0 

1500 

19/18 . 

•03440 

31-0 

900 

48-0 

1395 

7/14 . 

•03520 

32-0 

908 

49-0 

1390 

19/16 . 

•06130 

49-0 

800 

77-0 

1255 

19/14 . 

•09550 

70-0 

732 

110-0 

1150 

37/16 . 

•11900 

83-0 

695 

130-0 

1090 

19/12 . 

•16100 

100-0 

620 

170-0 

1055 

37/14 . 

•18600 

120-0 

645 

190-0 

1020 

61/15 . 

•25000 

150-0 

600 

240-0 

960 

61/14 . 

•30600 

170-0 

555 

290-0 

948 

37/12 . 

•31300 

180-0 

575 

300-0 

958 

61/12 . 

•51600 

260-0 

504 

450-0 

873 

91/12 . 

•77000 

350-0 

455 

620-0 

805 

91/11 . 

•98100 

420-0 

428 

740-0 

754 


1 Paper read before Section E of the St. Louis International Electrical Congress of 1904 
(“ Transactions,” Yol. II., p. 666); also Electrician, Vol. LIV., p. 964 (March 31st, 1905). 

148 



























THE HIGH TENSION TRANSMISSION SYSTEM 

Table XLY. 

Current Densities in Copper Wires Employed in Cables for 1,000 Volts and over 
according to the Rules of the German Society of Electricians. 


Cross Section of Conductor. 

Working 

Current. 

Current Density. 

Sq. mm. 

Sq. ins. 

Amperes. 

Amperes per 
sq. cm. 

Amperes per 
sq. in. 

1-5 

0-0023 

6 

400 

2580 

2 - 5 

0-0039 

10 

400 

2580 

4 

0-0062 

15 

375 

2420 

6 

0-0093 

20 

333 

2150 

10 

0-0155 

30 

300 

1930 

16 

0-0248 

40 

250 

1610 

25 

0-0388 

60 

240 

1550 

35 

0-0543 

80 

228 

1470 

50 

0-0775 

100 

200 

1290 

70 

0-109 

130 

185 

1190 

95 

0-147 

160 

169 

1090 

120 

0-186 

200 

167 

1075 

150 

0-233 

235 

157 

1010 

185 

0-287 

275 

149 

960 

240 

0-373 

330 

137 

884 


Several formulae have been proposed for calculating permissible current densities 
corresponding to a certain temperature rise. The Verband Deutscher Elektrotechniker 1 
and Teichmuller in the “ Elektrotechnische Zeitschrift ” for November 3rd, 1904, give 
involved formulae, taking account of the conductivity of the soil and the insulation on 
the cable. In Fig. 129 is given a set of curves 2 showing the relation between cross 
section of copper and permissible current for temperature rises of 25 degrees Cent, 
and 5 degrees Cent., calculated according to these formulae, for cables laid at a depth 
of 18 ins. in the eaith. On the same sheet appear two curves from experimental data 
for cables in air, which give an interesting comparison with the other curves. 

From the curves in Fig. 129 have been plotted those given in Fig. 130, which 
show current densities for different cross sections. 

The National Conduit and Cable Company, who supplied the cables for the 
Central London Railway, state the following conditions for three-core cables :_ 

For continuous operation with alternating current, 1,000 amperes per square 
inch. 

For 6 hours an increase of 30 per cent, in current density, and for 3 hours an 
increase of 50 per cent., is permissible under ordinary conditions, and a greater 
inciease under conditions which give the surrounding air a good circulation round 
the cables. The above increase of 30 per cent, would cause a rise in temperature of 
the copper of approximately 55 degrees Cent. (100 degrees F.) in 3 hours. 

Temperature Distribution in Cables. 

The temperature rise in the lead sheathing or the armouring is much smaller 
than that of the copper cores. The sheathing on paper-covered cables does not reach 

1 See “ Electrotechnischer Zeitschrift,” May 7th, 1903. 

2 For these curves we are indebted to Mr. A. L. Kavanagh. See paper on “ Manufacture and 
Design of Cables ” [Institution of Electrical Engineers (Students’ Section), 1905]. 

149 

























ELECTRIC RAILWAY ENGINEERING 


so high a temperature as on rubber-covered cables, because of the paper being a better 
heat insulator than rubber. 

Fig. 131 gives a good representation of the relative magnitudes of the temperature 
rise of the conductors and sheathing. This figure we reproduce, as well as Figs. 132 
and 133 1 , from the paper by L. A. Ferguson read before Section E of the St. Louis 



Fig. 129. Kavanagh’s Curves of Current Densities in Cables. 

A = Cable IS ins. underground, 25 degrees Cent. rise. 

T> _ 

tt tt tt it ft tt 

C = Cable in air, 25 degrees Cent. rise. 

D = Cable IS ins. underground, 50 degrees Cent. rise. 

E = 

J it tt tt It it it 

F = Cable in air. 50 degrees Cent. rise. 

G — I. E. E. Rules, 10 degrees Cent. rise. 


International Electrical Congress of 1904. Some interesting results, showing com¬ 
parisons between temperature rises of cables in conduits and in the air, are given in 
this paper, from which we quote the following paragraph :— 

“ Nearly all cables for underground work are insulated with either paper or 
rubber, and are lead-covered. For some purposes, such as the grounded side of street 
railway circuits or the neutral of Edison three-wire systems, bare copper is satisfactory. 

1 Figs. 132 and 133 are not precise reproductions, but are plotted from the curves as riven bv 
Ferguson, but in such groupings as to make them more useful. 

150 




































































THE HIGH TENSION TRANSMISSION SYSTEM 

Bare copper should not, however, be installed in the same duct with lead-covered 
cables. Paper-insulated cable is more generally used than rubber, on account of its 
lower first cost and also on account of its greater carrying capacity. Rubber cable 



will stand rougher use, and may be more easily handled in extremely cold weather, 
than paper cable. It is easier to protect the ends of rubber cables than those of 
paper, and for this reason rubber cable is sometimes used for mains and services on 
account of the large number of connections necessary for this work. It is not difficult, 

Hi 
























































































































ELECTRIC RAILWAY ENGINEERING 


•000020 

t. 

•000015 a . 

1 
« 
o 


however, to safely instal paper-insulated cable for this class of work, and it is much 

more satisfactory to do this, and thus carry 
only one kind of cable in stock. Paper- 
insulated cable is particularly suitable for 
feeders on account of its high carrying 
capacity. Within the past two years cable 
•ooooio ’ with varnished cambric insulation has been 
used for high-voltage work inside stations, 
and to a limited extent for underground work. 

“ Single-conductor cable is commonly 
used for low-tension feeders in sizes ranging 
from 250,000 circular mils, to 1,000,000 cir¬ 
cular mils. Considerable saving in feeders 
may be made by using two-conductor con¬ 
centric cable, with pressure wires laid up 
with the outer conductor. Concentric 
cables for feeders are used mostly in the 
1,000,000 circular mil. size. Its carrying 
capacity is less than that of two-conductor 
i.6oo 1.800 cables of the same size, and the cost is 

about the same. The saving is made in 
Fig. 131. Ferguson’s Tests of Tempera duet and manhole space, and in the cost 
ture Distribution in Cables. of i nsfca H a tion. 

“Figs. 132 and 133 show the carrying capacity of lead-covered paper-insulated 
cable in conduit and in air. These tests were made in a laboratory, the conduit 



800 1.000 


1,200 1 400 

Amperes. 


Cable /n Con c/a/C 


Cab/e /ri C/r. 



Figs. 132, 133. Ferguson’s Curves showing Temperature Bise in Cables. 

152 





















































































































THE HIGH TENSION TRANSMISSION SYSTEM 

consisting of a single duct of vitrified clay pipe surrounded with approximately 6 ins. 
of sand on all sides. The tests on 1,000,000 circular mils, two-conductor concentric 
cable, were made with the cable in the air. Concentric cable should be made with 
the inner conductor so much larger than the outer that the average loss in the two 
conductors will be the same. At maximum load the loss would be more in the 
inner than the outer conductor, and less in case of light load.” 

Cable Installation. 

For underground work, cables are laid in some form of conduit. The material 
of the conduit is generally a variety of earthenware. Vitrified clay pipes and ducts 
aie in most common use. Cement-lined iron pipe has been used in some cases. 
Earthenware conduits may be either of single or multiple duct construction, with 
either round or square ducts. The square duct is generally preferable on account 
of the gieatei ease with which the cables can be drawn in. In L. A. Ferguson’s 
St. Louis Congress paper, referred to above, the question of conduit construction is 
well considered, and the substance of the conclusions is embodied in the following 
paragraphs:— 

“ Various forms of ducts are on the market for underground work, vitrified clay 
tile being used much more than all other kinds of conduit. 

“ Multiple duct is furnished in sizes ranging from two to nine ducts, and in lengths 
ranging up to 6 ft., although the 6-ft. lengths are not made to any great extent, on 
account of the danger of warping; 3 ft. is the standard size for four and six-duct 
multiples ; nine-duct tile is difficult to handle, and four and six-duct sections are most 
generally used. There are two objections to the use of multiple duct as compared 
with single duct: first, between any two cables in one piece of multiple duct there is 
only one wall; second, it is not possible to break joints as with single-duct conduit. 
These two things increase the liability of a fire in one duct reaching cables in 
adjoining ducts. In single-duct construction, there are always two walls between 
adjacent cables, and all joints are broken, so that there is but very slight possibility of 
a burn-out in one cable reaching any adjoining cable. Single-duct construction is 
unquestionably the best, particularly for large companies, where a burn-out on a 
cable is liable to be severe on account of the large amount of power concentrated at 
that point. 

“ The first cost of single and multiple tile is approximately the same. The 
cost of installing multiple duct should be approximately 15 per cent, less per 
duct than for single duct. The weight of single-duct tile is about 20 per cent, 
more per duct foot than for four and six-duct multiples. The lower cost of installing 
multiple duct is due to the lower freight charges on account of the lesser weight, 
and also to the smaller cost for labour. It is usually necessary to employ a 
bricklayer for installing single-duct conduit, and multiple-duct may generally be 
installed with the better class of labourers. 

“ A good arrangement of ducts is secured by laying them not more than four 
wide and as high as necessary to obtain the required number of ducts. These 
ducts should be separated into two vertical rows where they enter the manhole, 
the separation being about 8 ins. The separating of the ducts should begin about 
5 ft. or 6 ft. back from the manhole. This arrangement gives two vertical rows 
of cables on each side of the manhole, and leaves them much easier to support 
and protect than would be the case with three or more vertical rows. With an 

153 


ELECTRIC RAILWAY ENGINEERING 



6 't■ r 

i ■*/ ", *1 /f K V, 

( * **, "► * *, -**i * 

\ " —• V «• ""V 

n* 


arrangement of ducts not more than four wide, no cable can have more than one 

other duct between it and the surrounding earth, 
thus permitting good radiation of heat.” 

Cable Work of the New York Subway. 

The cable work on the subway of the Inter¬ 
borough Eapid Transit Co. affords an interesting 
instance of modern methods. The following 
description is abstracted, by permission, from the 
Company's publication entitled “ The New York 
Subway: its Construction and Equipment ” : — 

“ From the power-house to the subway at 
58th Street and Broadway, two lines of conduit, 
each com- 



’ at ^ n /ef 

DUCT LINE ACROSS 58TH STREET 
32 DUCTS 


Fig. 134. New York Subway : 
Arrangement of Cable Ducts 
under Street. 


prising 

t h i r t y - 

two ducts, have been constructed. These 
conduits are located on opposite sides of the 
street. The arrangement of ducts is 8 X 4, 
as shown in Fig. 134. The location and 
arrangement of ducts along the line of the 
subway are illustrated in photographs in 
Figs. 135 and 136, which show respectively 
a section of ducts on one side of the 
subway between passenger stations, and a 
section of ducts and one side of the subway 
beneath the platform of a passenger station. 
From City Hall to 96th Street (except 
through the Park Avenue tunnel) sixty-four 
ducts are provided on each side of the 
subway. North of 96th Street, sixty-four 
ducts are provided for the west-side lines, 
and an equal number for the east-side lines. 
Between passenger stations, these ducts help 
to form the side walls of the subway, and 
are arranged thirty-two ducts high and two 
ducts wide as in Fig. 135. Beneath the 
platforms of passenger stations the arrange¬ 
ment is somewhat varied because of local 
obstructions, such as pipes, sewers, etc., of 
which it was necessary to take account in 
the construction of the stations. The plan 
shown in Fig. 136 is, however, typical. 

“ The necessity of passing the cables 
from the 32 X 2 arrangement of ducts aloim 
the side of the tunnel to 8 X 8 and 16 X 4 
arrangement of ducts beneath the passenger 
platforms, involves serious difficulties in the 
proper support and protection of cables 

154 



'• Y r J ^ % ^ - * - "S' >• €*'* 


Fig. 135. New York Subway: Location 
and Arrangement of Cable Ducts inside 
Wall of Tunnel. 































































































THE HIGH TENSION TRANSMISSION SYSTEM 

in manholes at the ends of the station platforms. In order to minimise the 
risk of interruption of service due to possible damage to a considerable number 
of cables in one of these manholes, resulting from short circuit in a single 
cable, all cables, except at the joints, are covered with two layers of asbestos, 
a og re g a fi n g a full quarter-inch in thickness. This asbestos is specially prepared, 
and is applied by wrapping the cable with two strips, each 3 ins. in width, 
the outer strip covering the line of junction between adjacent spirals of the 
inner strip, the whole when in place being impregnated with a solution of 
silicate of soda. The joints themselves are covered with two layers of asbestos held 
in place by steel tape applied spirally. To distribute the strains upon the cables 
in manholes, radial supports of various curvatures, and made of malleable cast 
iron, are used. The photograph in Fig. 137 illustrates the arrangement of cables 
in one of these manholes. 

“In order to further diminish the risk of interruption of the service due to 
failure of power supply, each sub-station south of 96th Street receives its alternating 
current from the power-house through cables carried on opposite sides of the 
subway. To protect the lead 
sheaths of the cables against 
damage by electrolysis, rubber 
insulating pieces one-sixth of an 
inch in thickness are placed be¬ 
tween the sheaths and the iron 
bracket supports in the manholes. 

“ The cables used for con¬ 
veying energy from the power¬ 
house to the several sub-stations, 
aggregate approximately 150 miles 
in length. The cable used for 
this purpose comprises three 
stranded copper conductors, each 
of which contains nineteen wires, 
and the diameter of the stranded 
conductor thus formed is O'dO of an 
inch. Paper insulation is employed, and the triple cable is enclosed in a lead sheath 
6 9 5 of an inch thick. Each conductor is separated from its neighbours and from 
the lead sheath by insulation of treated paper T 7 e of an inch in thickness. The 
outside diameter of the cables is 2§ of an inch, and the weight 8J lbs. per lineal foot. 
In the factories the cable as manufactured was cut into lengths corresponding to 
the distance between manholes, and each length subjected to severe tests, including 
application to the insulation of an alternating current potential of 30,000 volts for 
a period of 30 minutes. These cables were installed under the supervision of 
the Interborough Co.’s engineers, and, after jointing, each complete cable from 
power-house to sub-station was tested by applying an alternating potential of 
30,000 volts for 30 minutes between each conductor and its neighbours, and 
between each conductor and the lead sheath. The photograph in Fig. 138 
illustrates this cable.” 

Another method frequently adopted in railway work is to run the feeders along 
beside the track, supporting them on cast iron brackets, with semicircular channelled 
lugs fixed on to the walls of the tunnel, or on to wooden stakes driven vertically 

155 



DUCTS UNDER PASSENGER STATION PLATFORM 
64 DUCTS 

Fig. 136. New York Subway : Arrangement of 
Cable Ducts under Passenger Station. 


































ELECTRIC RAILWAY ENGINEERING 


in the ground. In this way several cables can he efficiently laid one above the 
other, and the whole group covered in with a protecting cover of sheet iron. 

Examples of this practice are given in the case of the Central London Railway 

and the London Underground Electric Rail¬ 
ways, of which systems we shall now give 
some particulars. 

Cable Work of the Central London 
Railway. 

The high tension cables were fur¬ 
nished by the National Conduit and Cable 
Co. of New York. They are three-core 
cables, paper-insulated, and were tested at 
the works to 15,000 R.M.S. volts between 
the different cores and from cores to earth. 
The normal working voltage is 5,000 volts 
between cores. 

The 5,000-volt current leaves the 
power-house by four independent lead- 
covered three-core cables. From the 
power-house to Notting Hill Gate each 
core has a total copper cross-section of 
‘1875 sq. in. (121 sq. mm.). The cables, 
two in the down tunnel and two in the 
up tunnel, are laid upon cast-iron brackets 
at the side of the tunnel, and are protected 
by curved sheet iron plates throughout 
the length. The arrangement is shown 
in Fig. 189. 

At Notting Hill Gate sub-station, three 
87/16 cables are carried from the three 
cores of each of the four cables, the joints 
being made and protected by an ebonite 
cylinder filled in with paraffin. 

From Notting Hill Gate to Marble 
Arch the cross-section of the core is 
reduced to 0‘125 sq. in. (80‘5 sq. mm.). At 
Marble Arch sub-station, one of the cables in each tunnel is discontinued. The other 
two proceed with the 0‘125 sq. in. (80‘5 sq. mm.) cross-section to the Post-office sub¬ 
station, where they are carried directly to the feeder panels. Here the high tension 
line terminates. 

The following is abstracted from the specification to which the cables were 
built:— 

Each cable consists of three separately insulated conductors, paper-insulated 
and lead-sheathed. Each conductor is insulated with paper impregnated with 
resinous oil to a thickness of ^ in. (0'317 cm.), twisted together with a lead of 
18 ins. and the whole surrounded by additional impregnated paper of a minimum 
thickness of ^ in. (0‘317 cm.), so that the minimum thickness between cores or 

156 



Fig. 137. New York Subway : Arrange¬ 
ment of Cables in Manhole. 










THE HIGH TENSION TRANSMISSION SYSTEM 

between core and sheath is ^ in. (0*634 cm.). The cable is protected by pure lead 

sheathing $ in. thick. Sections through these cables are shown in Fig. 143 (cables 
Nos. 2 and 8). b 

The resistance per conductor per 1,000 ft. of finished cable at a temperature 
of 60 degrees F. was not to exceed 0-0645 ohm for 0-125 sq. in. section of copper and 
0-0430 ohm for 0-1875 sq.. in. section of copper. The cables were tested with a 
pressure of 15,000 effective volts alternating, between adjacent conductors and 
between each conductor and lead covering, at the makers’ works. When laid and 



Fig. 13S. New York Subway: Cable. 


Section oP 

Cable Support & Shield 



Fig. 139. Arrangement of Central 
London Railway Cables. 


jointed the cable was subjected to an effective alternating voltage of 10,000 volts 
at 25 cycles for 1 hour. 

The cables were manufactured in lengths wound on the ordinary drums, of 
convenient diameter for working in the tunnels. The diameter of the tunnels is 
11 ft. 6 ins., and the clear height from level of rails 9 ft. 

I here are no manufacturers’ joints in the lengths supplied. 

Table XIA I. gives particulars of the cables as laid :— 


Table XLYI. 


Particulars of Central London Railway High Tension Cables. 



®"2 
g 5 

<& 

CD 

— IO 

<♦-1 • 
o,2S 

A 

Sectional Area. 


A 60 


o 

a o 

0. O 


! Distance bet 
j Stations — Y 

«*- 'S 
° 8 
<3 p 

'2 c 
~ o 

£ 

Total Lengt 
Cable — Ya 

Square 

Inches. 

Circular 

Mils. 

Number < 
Strands. 

Area of eai 
Strand- 
Circular Mi 

Overall 

Diameter 

Resistance of 
Core per l,( 
Yards. 

Generating Station to 
Notting Hill Gate Sub¬ 
station .... 

2530 

4 

10,120 

0-1875 

239,000 

37 

6460 

2F 

1 15" 

0-130 

Notting Hill Gate Sub¬ 
station to Marble Arch 
Sub-station . 

3050 

4 

12,200 

0-125 

159,200 

19 

8380 

0-195 

Marble Arch Sub-station to 
Post-office Sub-station . 

4590 

2 

9180 

0-125 

159,200 

19 

8380 

1 IS" 

-^io 

0-195 


157 















































ELECTRIC RAILWAY ENGINEERING 


At the time of making the insulation tests, the capacity current was measured, 
with the following results :— 

Test pressure ...... 10,000 volts. 

Periodicity .25 cycles per second. 

Two cables were tested in parallel, i.e., one core from each, connected together 
and tested to the other four cores connected to sheaths. 

Power House switchboard to Notting Hill Gate switchboard . . ■ 1'9 amperes. 

,, ,, to Marble Arch switchboard .... 3’7 ,, 

,, ,, to Post-office switchboard . . . . 4'7 ,, 

In Fig. 1-13, cables Nos. 2 and 3, are given sections of the tw T o sizes of cables 
employed. Table XLVII. gives a tabular statement of the capacity per mile between 
cores, and from cores to lead. These values were deduced from the tests already 
referred to. 

Table XL VII. 


Dielectric Capacity of Central London Railway Cables. 



Capacity per Mile in 
Microfarad. 

One core and other tw y o cores and sheath ..... 

0-38 

One core and other two cores ........ 

0-32 

One core and one other core ........ 

0-23 


Other data of interest regarding these high tension cables are tabulated below:— 


Table XLYIII. 

Weights and Dimensions of Central London Railway High Tension Cables. 



•1875 Square Inch 

•125 Square Inch 


Cores. 

Cores. 

Pounds copper per cable per 1,000 ft. length . 

2140 

1425 

Pounds insulation per cable 1,000 ft. length . 

1090 

995 

Pounds lead per cable per 1,000 ft. length 

3870 

3480 

Pounds weight complete cable per 1,000 ft. length 

7100 

5900 

Pounds weight complete cable per cubic inch 

0-166 

0-165 

Average specific gravity complete cable 

4-6 

4-6 

Total weight of copper in all high tension cables . 

78’4 tons. 

Total weight of all high tension cables complete 

290 

>> 

Total length of all high tension cables .... 

19‘6 miles 


Outside diameter ........ 

2^ ins., 1- 

rf ins - 


Cable Work of the London Underground Electric Railways. 

District Railway. 

The contract for cables on this railway w-as divided between several manu¬ 
facturers, the British Insulated and Helsby Cables, Ltd., having the largest portion. 

Each manufacturer had several sections in different parts of the system. 

The total length of high tension cable employed on the system is about 207 miles, 
exclusive of 78 miles laid dow T n for the Great Northern and Brompton, Baker Street 
and aterloo, and Charing Cross and Hampstead Railways, and between Lot’s Road 
and Earl’s Court, and Earl’s Court and Charing Cross. 

158 
























THE HIGH TENSION TRANSMISSION SYSTEM 


The total length of cable supplying high tension current from Lot’s Road to all 
railways fed, will be about 363 miles. 

All the cables supplied by the British Insulated and Helsby Cables, Ltd., for 
high tension current, are three-core, paper-insulated and lead-covered, for a working 
pressure of 11,000 volts. The cables were supplied in three sizes, particulars of which 
are given in the following table:— 

Table XLIX. 

Particulars of London Underground Railways High Tension Cables. 



Size of Cable—L.S.G. 



No. 37/15. 

No. 37/14. 

No. 37/13. 

Sectional area of each conductor, square inch 
Maximum resistance of each conductor per 1,000 ft. 

0T5 

0-19 

0-25 

at 60° F. ohm .... 

0'054 

0044 

0-034 

Thickness of insulation between conductors 

Thickness of insulation between conductors and 

0'4375 in. 

0-4375 in. 

0-4375 in. 

earth ........ 

0-4375 in. 

0-4375 in. 

0-4375 in. 

Thickness of each insulation paper . 

O'OOo in. 

0 - 005 in. 

0'005 in. 

Thickness of lead covering ... 

04875 in. 

0-1875 in. 

0‘1875 in. 

Approximate overall diameter of finished cable 

2-65 ins. 

2-78 ins. 

2-94 ins. 

Approximate diameter of finished joints . 
Approximate maximum insulation resistance per 

4 ins. 

4-2 ins. 

4-4 ins. 

mile, at 60" F. (megohms) ..... 

500 

500 

500 


The thickness of the insulation between the conductors, as well as between each 
conductor and earth, is 0437 in. 

The maximum insulation resistance per mile is 500 megohms at 60 degrees F. 
The specification provided that the cables should stand 33,000 volts after being 



Fig. 140. District Railway: Cables mounted ox Wall, showing Joints. 

immersed in water for 24 hours, and it is understood that they have withstood 
40,000 volts in Works tests. 1 

In all, some 200 miles of cable were supplied by the British Insulated and Helsby 
Cables, Ltd. 

1 See Light Bailway and Tramway Journal , February 3rd. 1905. 

159 





























ELECTRIC RAILWAY ENGINEERING 


The work of laying or fixing sections of cable was very arduous, as all the tunnel 

portions had to be laid or drawn into ducts during a 
working night of 2f hours, this being the only time 



during which no trains were running. 


than 6 months, 
other than the 




o_ 


> 


The work was carried out in less 
in spite of late deliveries of material 
cables themselves. 

The work of jointing the cables in the British 
Insulated and Helsby sections was very heavy, there 
being in all 1,330 joints. These were completed in an 
average time of 5 hours per joint. The joints made by 
the British Insulated and Helsby Cables are insulated 
with tape boiled in resin oil. Out of 110 miles of cable, 
106 miles were laid in 540 hours. The average working 
week being 19 hours, this period was spread over 
6 months. The cables were carried in racks at places 
where the joints occur, the joints being staggered, as 
shown in Fig. 140. 

The cables supplied by Messrs. Callender’s Cable 
and Construction Co., are all three-core, paper-insulated, 
and lead-covered. They are intended for a working 
pressure of 11,000 volts at 33^ periods. The cables 
were tested at the factory at 33,000 volts between 
adjacent cores, and between each core and earth. They 
were also tested with 22,000 volts for 1 hour between 
earth and conductors when laid. These cables were 
supplied in two sizes, each size having three cores of 
0*15 sq. in. and 0*25 sq. in. respectively. 

The weight of the larger cable is about 28 tons per 
mile, with a capacity of about 0*29 microfarad per mile. 
The smaller cable weighs 25 tons per mile, and has a 
capacity of 0*354 microfarad per mile. 

These cables are drawn into glazed earthenware 
pipes of 3^ ins. internal diameter, the pipes being 
laid in concrete. 

The average distance between draw-pits is about 
350 ft., with a maximum distance of 570 ft. The 
following description of the method of making a joint 
may be interesting 1 :— 

The lead and insulation of each cable is cut back, 
and the ends of the three copper cores of each cable 
are then cut so as to “ butt ” solid against each other ; 
the cores, however, are cut in such a manner that 
the joints are stepped. Over the ends of the copper 
cores are slipped copper ferrules, which are sweated on. 
These ferrules are then lapped with high insulation 
linen tape, and painted with composition. After each joint has been made, three 






A 

(—1 

O 

i 

W 

t-J 

n 

<1 

o 

A 

O 

w 

£ 

W 

EH 

H 

3 


O 

o 

H 

H 

A 

o 

HH 

H 

C 

W 

m 

£ 
►—I 

Ph 


H 

m 




6C 

• *H 


1 See Light Railway and Tramway Journal, February 3rd, 1905. 

160 














































































































THE HIGH TENSION TRANSMISSION SYSTEM 

lings, of high-insulation tape are wrapped around to keep the cores in their proper 
position. A lead sleeve, which has previously been slipped over the end of one 
of the cables, is then placed in position, and wiped down on to a lead ring at each 
end. The sleeve is then filled with special lead-sleeve compound, and the hole 



!ig. 142. District Kailway: Manhole in Transmission Line under Construction. 

through which the compound has been poured is then sweated solid. A section 
through a joint is shown in Fig. 141. 

Fig. 142 gives a view of a manhole in the transmission line during construction, 
showing the cable ducts. 

Metropolitan R ail way. 

All the cables for the Metropolitan Railway were supplied and laid by the British 
Insulated and Helsby Cables, Ltd. The cables have three conductors, are paper- 
insulated and lead-covered. The lead is protected by insulating material, and the 
whole is then armoured by round galvanised steel wires of 0-104 in. diameter. The 
overall diameter of the cable is about 8 inches. All the cables were tested at the 
works at 33,000 volts, and again at 22,000 volts, or double the working pressure 
when laid. 


E.R.E. 


161 


M 














ELECTRIC RAILWAY ENGINEERING 


In all, there are 9 miles of cable of 0T5 sq. in. cross section ; 

„ „ 14 „ 0-20 

>> 24 ,, ,, 0 25 ,, ,, 

„ ,, 25 „ 0-10 

Outside the stations, the cables are laid solid in wooden troughs run in with 

pitch. At bridges, etc., they are drawn into pipes. 

The low tension cables are connected to the rails by low tension rubber insulated 
cables, which are partly in ducts and partly in troughs. 

In Fig. 143 are given drawings of sections through several high tension cables, 

including the Central London Railway and Metropolitan 
District Railway cables already described. 

Fig. 144 shows a section through Henley’s Patent 
“ Laminae” Conductor Cable, which is a recent develop¬ 
ment in three-core cables; the cores are built up of a 
number of Y-shaped copper strips laid up one within 
the other. 

In Tables L., LI., LII., and LIII. are given the 
Engineering Standards Committee’s standard thick¬ 
nesses of insulation and lead sheathing for three-core 
and concentric cables, paper-insulated (Tables L. and 
LI.) and rubber-insulated (Tables LII. and LIII.). 
These tables are for voltages from 2,200 to 11,000, but 
we are only concerned here with extra high pressures, 
i.e., above 5,000 volts. We have inserted these tables 
exactly as they stand in the committee’s report, because there is much useful informa¬ 
tion in them, and we wish to bring into prominence such work in the direction of 
standardisation on a rational basis. 



Fig. 144. Section of Hen¬ 
ley’s Patent Laminae Con¬ 
ductor Three-core Cable. 


Table L. 

Engineering Standards Committee''s Table of Thicknesses of Insulation for Paper- 
Insulated Concentric Cables for Pressures exceeding 2,200 Volts. 


II 

[High Pressure Concentric. 
Working Pressure. 


Nominal 
Area of 
Conduc¬ 
tors. 

2,200 Volts. 

1 Dielectric 
Inner. 

: Dielectric 
Earthed 
Outer. 

Lead. 

Square 




Inch. 

Inch. 

Inch. 

Inch. 

•025 

•12 

•08 

•08 

•050 

•12 

•08 

•09 

•075 

■12 

•08 

•09 

•100 

13 

•09 

•10 

•125 

•13 

•09 

•10 

•150 

•13 

•09 

•11 

•200 

•13 

•09 

•11 

•250 

•14 

•10 

•12 


Test at Works 10,000 Volts 
for half-an-hour. 

Test when laid and jointed 
4,000 Volts for half-an-hour. 


Extra High Pressure Concentric. 
Working Pressures. 


3,300 Volts. 


6,600 Volts. 


11,000 Volts. 


Dielectric 

Inner. 

Dielectric 

Earthed 

Outer. 

Lead. 

Dielectric 

Inner. 

Dielectric 

Earthed 

Outer. 

Lead. 

Dielectric 

Inner. 

Dielectric 

Earthed 

Outer. 

Lead. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

•15 

•09 

•09 

•23 

•10 

•10 

•35 

•12 

•12 

•15 

•09 

•10 

•23 

•10 

•11 

•35 

•12 

•13 

•15 

•09 

•10 

•23 

•10 

•12 

•35 

•12 

•14 

•16 

•10 

•10 

•24 

•11 

•12 

•36 

•12 

•14 

•16 

•10 

•n 

•24 

•11 

•13 

•36 

•12 

•14 

•16 

•11 

•11 

•24 

•12 

•13 

•36 

•12 

•15 

•16 

•11 

•12 

•24 

•12 

•13 

•36 

•12 

•15 

•17 

•11 

•13 

•25 

•12 

•14 

•37 

•12 

■16 

Test at Works:—12,000 Volts 
for half-an-hour. 

Test at Works:—20,000 Volts 
for half-an-hour. 

Test at Works 30,000 Volts 
for half-an-hour. 

Test when laid and jointed :— 

Test when laid and jointed:— 

Test when laid and jointed:— 

6,000 Volts for half-an-hour. 

12,000 Volts for half-an-hour. 

20,000 Volts for hal'f-an-hour. 


162 
























































American Cables ^ 



■4600 Yo/t3 - 0'/&3Sy.Inf/07Sf him) 


Central London B/wy. 



5000 Volts ■ 0725 Sain fjQSohim) 
per Core 


Central London Cl try. 



5000 Celts - O'/Q^p Scfln ^0 


Manchester Cob/e 


Lancashire <$ Yorkshire (able. 


Baker Street <2Waterloo Bh-ry. 




0500 Yo/ts-O'/5SqInf06 T7Sa/^J 

per Cbre 


10000 Co/ts;045Sy.In-{3677S<f tom) 
per Core 



HOOO kolts - o '/5SgIn(h4- 0 St). him) 


Mem York Sabi ray 


Metropolitan ID/ strict tf/ny 


Callenders Lead Sheathed Cable 
with Steel h/ire Heard of Trade Shie/d 




Caper 7 Lfa 
■Lead ~?/6 


I1000 Colts -CIJ2 So In (HZ So. thm) 

per Cote L 


HOOO Volts O'25Sain(f62 S) him) 

per Care 



HOOO Volts 0-25SgJn (l6Z Sg. IhmJ 


Callenders Lead Sheathed Cable 
with Copper Tape Board of TradeSheld 



A 


men can 


Cables ^ 


American Cables 


•* 




HOOO Co/ts • 025SgIn//<52S<f h,m ) 


25000Vo/ts 0036Sajnf35-5So hrn) 
pier Core 


tfubber-^z 

lute 

tftuhber- 5 ? 
Lead * ^8 


35000 Volts 0036 Sr) In f-355 S) him) 
per Core 


Eig. 143 . Sections of various High Tension Cables. 



































































































































































THE HIGH TENSION TRANSMISSION SYSTEM 


Table LI. 


Engineering Standards Committee's Table oj Thicknesses of Insulation for Paper 
Insulated Three-Core Cables for Pressures exceeding 2,200 Volts. 


Nominal 
Area of 
Conduc¬ 
tors, 


Square 

inch. 

025 

050 

075 

100 

125 

150 

200 

250 


High Pressure Three-Core. 
Working Pressure. 



Extra High Pressure Three-Core. 
Working Pressures. 



2,200 Volts. 

— 


3,300 Volls. 


6,600 Volts. 

I 


11,000 Volts. 


Dielectric 
Between 
[ and 

Outside. 

Dielectric 
Outer on 
Star 

Winding 

with 

Centre 

Earthed. 

Lead. 

Dielectric 

Between 

and 

Outside. 

Dielectric 
Outer on 
Star 
Winding 
with 
Centre 
Earthed. 

Lead. 

Dielectric 

Between 

and 

Outside. 

Dielectric 
Outer on 
Star 

Winding 

with 

Centre 

Earthed. 

Lead. 

j Dielectric 
[ Between 
and 

j Outside. 

Dielectric 
Outer on 
Star 

Winding 

with; 

Centre 

Earthed. 

Lead. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

•13 

•10 

•08 

15 

•12 

•09 

•23 

•17 

•10 

•35 

•23 

•12 

■13 

•10 

•09 

•15 

•12 

•10 

•23 

•17 

•11 

•35 

•23 

•13 

•13 

•10 

•10 

15 

•12 

•10 

•23 

•17 

12 

•35 

•23 

•13 

•14 

•11 

•11 

•16 

•13 

•11 

•24 

•18 

•12 

•36 

•24 

14 

•14 

•11 

•11 

•16 

•13 

•12 

•24 

•18 

•13 

•36 

•24 

•14 

14 

•11 

•12 

16 

•13 

•12 

•24 

•18 

•13 

•36 

•24 

•15 

•14 

•11 

•13 

16 

•13 

•13 

•24 

•18 

•14 

•36 

•24 

•16 

•15 

■12 

•13 

•17 

•14 

•14 

•25 

•19 

•15 

•37 

•25 

•17 

Teat at Works:—10,000 Volts j 
for half-an-hour. 

Test at Works :—12,000 Volts 
for half-an-hour. 

Test at Works20,000 Volts 
for half-an-hour. 

Test at Works :—30,000 Volts 
for half-an-hour. 

Test when laid and jointed :— | 

Test when laid and jointed: — 

Test when laid and jointed :— 

Test when laid and jointed:— 

4,000 Volts for half-an-hour. ; 

0,000 Volts for half-an-hour. 

12,000 Volts for half-an-hour. 

20,000 Volts for half-an-hour. 


Table LII. 

Engineering Standards Committee's Table of Thicknesses of Insulation for Rubber- 
Insulated Concentric Underground Cables for Pressures exceeding 660 Volts. 



From 660 to 

2,200 Volts. 

J From 2,200 to 3,300 Volts. 

From 3,300 to 6,600 Volts. 

j From 6,600 to 11,000 Volts. 

Nominal 
Area of 
Conduc- 

Inner 

Di¬ 

electric. 

Outer 

Dielectric. 


Inner 

Di¬ 

electric. 

Outer 

Dielectric. 


Inner 

Di- 

electric. 

Outer 

Dielectric. 


Inner 

Di¬ 

electric. 

Outer 

Dielectric. 


tors. 

Earthed. 

Not 

Earthed. 

Lead. 

Earthed. 


Lead. 

Earthed. 

Not 

Earthed. 

Lead. 

Earthed. 

Not 

Earthed. 

Lead. 

Square 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

•025 

■11 

•07 

•11 

•08 

•13 

•08 

•13 

■08 

•20 

•09 

•20 

•09 

•29 

•10 

•29 

•10 

•050 

•11 

•07 

•11 

•09 

13 

•08 

•13 

•09 

•20 

09 

•20 

•10 

•29 

•10 

•29 

•10 

•075 

12 

•08 

12 

•09 

■14 

•09 

•14 

•10 

•21 

•10 

•21 

•10 

•30 

■11 

•30 

•11 

•100 

12 

•08 

•12 

•10 

•14 

■09 

■14 

•10 

•21 

•10 

•21 

•11 

•30 

•11 

•30 

•11 

•125 

•12 

•08 

•12 

•10 

•14 

•09 

•14 

•10 

•21 

•10 

•21 

•11 

•30 

•11 

•30 

•12 

•150 

•13 

•09 

•13 

•11 

•15 

•10 

•15 

•11 

•22 

•11 

•22 

•12 

•31 

•12 

•31 

•12 

•200 

•13 

•09 

•13 

•11 

15 

•10 

•15 

•11 

■22 

•11 

•22 

•12 

■31 

•12 

•31 

•13 

•250 j 

13 

•09 

•13 

•12 

15 

•10 

-15 j 

•12 , 

•22 

•11 

•22 

•13 

•31 

•12 

•31 

•13 


1 6 




M 2 






















































































































































ELECTRIC RAILWAY ENGINEERING 


Table LIII. 


Engineering Standards Committee’s Table of Thicknesses of Insulation for Rubber- 
Insulated Three-Core Underground Cables for Pressures exceeding 660 Volts. 


Nominal 

From G60 to 2,200 Volts. 

From 2,200 to 3,300 Volts. 

From 3,300 to 6,600 Volts. 

From 6,600 to 11,000 Volts. 

Area of 
Conductors. 

Dielectric on 
each Core. 

Lead. 

Dielectric on 
each Core. 

Lead. 

Dielectric on 
each Core. 

Lead. 

Dielectric on 
each Core. 

Lead. 

Square Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

•025 

•11 

•09 

T3 

TO 

•20 

•11 

•29 

•12 

•050 

•11 

TO 

•13 

•11 

•20 

•12 

•29 

T3 

•075 

•12 

•11 

•14 

T1 

•21 

T3 

•30 

T4 

•100 

•12 

•12 

•14 

•12 

•21 

•13 

•30 

T5 

•125 

•12 

•12 

•14 

•12 

•21 

T4 

•30 

•15 

•150 

T3 

T3 

T5 

•13 

•22 

•14 

•31 

•16 

•200 

•13 

T3 

T5 

•14 

•22 

T5 

•31 

T7 

•250 

•13 

•14 

T5 

•14 

•22 

•16 

•31 

T7 


The following are further abstracts from the Engineering Standards Committee’s 
report:— 

The dielectric and lead on all conductors, whether mains or pilot wires, smaller 
than 0'025 sq. in., shall have the thicknesses given for 0'025 sq. in. All intermediate 
sizes shall have the thicknesses given for the next larger size on the list. 

Twin cables shall have the same thicknesses as three-core cables. 

The allowable variation in radial thicknesses of dielectric and lead at any point 
shall be 10 per cent, below the standard minimum thicknesses given in the table, but 
the mean of the thicknesses shall be at least that specified. 

The standard armouring to be as follows :— 

For cables below 050 in. diameter over lead, galvanised steel wires 0072 in. diameter. 

For cables from 0’50 in. to 1 in. over lead, two layers of compound steel tape, each 0'030 in. 
thick. 

For cables from 1 - 01 in. to 2 ins. diameter, two layers of compound steel tape, each 0040 in. 
thick. 

Above 2 ins. diameter, by two laj'ers of compound steel tape, each 0 - 060 in. thick. 

The standard thicknesses of jute serving, when applied to diameters less than 0 - 50 in., to be 
0-06 in., and for larger diameters 0T0 in. 

All test pressures may be applied either with alternating or direct current, the 
former to be at the standard frequency. 

The pressure tests for the cables in these tables shall be as follows :— 


Working Pressure. 

Test at Works. 

Test when laid and 
jointed. 

Pressure applied for 
half an hour. 

Pressure applied for 
half an hour. 

Volts. 

Volts. 

Volts. 

2/200 

10,000 

4,000 

3,300 

12,000 

6,000 

6,600 

20,000 

12,000 

11,000 

30,000 

20,000 


164 













































THE HIGH TENSION TRANSMISSION SYSTEM 


Overhead High Tension Lines. 

Even in England there is a tendency to employ overhead high tension lines in 
certain cases, such, for instance, as where a railway can use its own right of way. 
Wlieie an overhead high tension transmission line is employed, some very different 
questions present themselves for solution, and they may be conveniently treated as 
follows :— 


^ ► = received voltage at end of transmission line. Then the phase 

relations of the voltage and current components are as indicated by the following vectors 

k 

= current drawn from transmission line leading received voltage by 
90 degrees; 

“ ► = current drawn from transmission line in phase with received voltage ; 




— current drawn from transmission line lagging 90 degrees behind received 
voltage. 


Before proceeding with the estimation, the current drawn from the transmission 
line should he resolved into the “ energy ” component and the “ wattless ” component. 


“ Energy ” component = 


“ watless ” component = 


or 


voltage required for sending a leading wattless current through a resist¬ 


ance ; 


voltage required for sending an energy current through a resistance 


— voltage required for sending a lagging wattless current through a resist¬ 
ance. 

W 

- = voltage required for sending a leading wattless current through an 
( t ^ inductance ; 

= voltage required for sending an energy current through an inductance ; 

M ► = voltage required for sending a lagging wattless current through an 

inductance. 


In the above it will be noted that the electromotive force is in phase with the 
current when driving it through a resistance, and leads it by 90 degrees when driving 
it through an inductance. 

In order to obtain at the end of the line the desired “received voltage ”— 


Received voltage—- 

some or all of the above component voltages (according to the nature of 
the transmission line) have to be calculated, and combined with the received 
















ELECTRIC RAILWAY ENGINEERING 


voltage, which must be supplied at the source. Thus in the following 
diagram— 



a b = voltage required at the receiving end of the transmission line ; 
b c = voltage required for sending leading wattless current 1 through line resistance ; 
c d = voltage required for sending leading wattless current 1 through line inductance ; 
d e — voltage required for sending energy current through line resistance ; 
e f = voltage required for sending energy current through liue inductance ; 
f g = voltage required for sending lagging wattless current through line resistance; 
g li = voltage required for sending lagging wattless current through line inductance; 
a li = voltage required to be generated. 

Table LIV. gives resistances for calculating the resistance voltages. 

Table LY. gives reactances for calculating the reactance voltages. 

Table LYI. gives the capacity and corresponding charging current per unit of 
length. 

Regarding the charging current, it should be pointed out that this is merely a 

function of the size of conductors, distance apart, voltage, and periodicity, and is 

independent of the load, being, in fact, always the same as at open circuit. 

• , 2 7 r x cycles per second X voltage X capacity in microfarads 

Charging current =- ——^^^ - 

10 6 . 

It has been found to be sufficiently accurate to regard the charging current per 
unit of length of line as the same at all points of the line. Hence, in calculating the 
voltage due to the charging current across resistance and reactance of line, one may 
take half the total charging current through the entire resistance and reactance. 

The use of the preceding rules and tables is best illustrated by an example. 

Example. 

Three-phase transmission plant. 

Power to be delivered at full load = 9,000 kilowatts. 

Power factor at full load = ’9 for delivered energy. 

Length of line = 100 kilometres. 

Periodicity = 50 cycles per second. 

Yolts between lines = 40,000 at receiving end. 

Yolts per phase = 23,100 at receiving end. 

Allow 3 per cent, reactance voltage for step-up transformers. 

Allow 3 per cent, reactance voltage for step-down transformers. 

Conductors of transmission line arranged on the three corners of an equilateral 
triangle. 

Distance between conductors = 100 centimetres. 

Cross section of conductor = 75 square millimetres. 

Diameter of conductor = 9'77 millimetres. 

From Table L1Y.—Resistance per kilometre = '229 ohm. 

From Table LY.—Reactance per kilometre = '353 ohm. 

From Table LYI.—Charging current per kilometre at 10,000 volts = '0189 ampere. 

1 Often charging current. 

166 









THE HIGH TENSION TRANSMISSION SYSTEM 


Table LIY. 


Resistances and Weights of Copper Conductors of various Sizes. 


Cross-section 
of Conductor 
in Square 
Millimetres. 

Diameter of 
Conductor in 
Millimetres. 

Resistance of 
Conductor in 
Ohms per 
Kilometre at 
20° Centi¬ 
grade. 

Weight of 
Conductor in 
Kilogrammes 
per Kilometre. 

Cross-section 
of Conductor 
in Square 
Millimetres. 

Diameter of 
Conductor in 
Millimetres. 

Resistance of 
Conductor in 
Ohms per 
Kilometre at 
20° Centi¬ 
grade. 

Weight of 
Conductor in 
Kilogrammes 
per Kilometre. 

20 

5-04 

•860 

178 

90 

10-7 

•191 

801 

25 

5 64 

•688 

223 

95 

11 

•181 

845 

30 

6-19 

•574 

267 

100 

11-3 

•172 

890 

35 

6 - 67 

•492 

312 

110 

11-8 

•156 

930 

40 

7-12 

•430 

356 

120 

12-4 

•143 

1068 

45 

7 - 57 

•382 

401 

130 

12-9 

•132 

1158 

50 

7-97 

•344 

445 

140 

13-4 

•123 

1246 

00 

8'36 

•313 

490 

150 

13-8 

•115 

1335 

60 

8-75 

•287 

534 

160 

14-3 

•108 

1424 

65 

9-09 

•265 

578 

170 

14-7 

•101 

1512 

70 

9-43 

•246 

624 

180 

15-1 

•096 

1602 

75 

9-77 

•229 

668 

190 

15-6 

•091 

1690 

80 

10-1 

•215 

712 

200 

16-0 

•086 

1780 

85 

10-4 

•202 

756 






Table LY. 


Inductances and Reactances of Copper Conductors. 


^-section of Conductor 
Square Millimetres. 

Inductance in Henrys of each of the Three Conductors of a 
Three-phase Transmission Line, per Kilometre of Length ot 
Line, when the Conductors are arranged at the Three Corners 
of an Equilateral Triangle. 

Distance between Centres of any Two Conductors in 
Centimetres. 

0 

0 

aa 

'C X 

6 s 

U-> — 

<D 

Reactance in Ohms at 50 Cycles per 
Second, of each of the Three Conductors 
of a Three-phase Transmission Line per 
Kilometre of Length of Line when the 
Conductors are arranged at the Three 
Corners of an Equilateral Triangle. 

Distance between Centres of any Two 
Conductors in Centimetres. 

-section of Conductor | 
Square Millimetres. 

0.5 

O 

30. 

40. 

60. 

so. 

100. 

120. 

140. 

- 

30. 

40. 60. 

80. 

100. 

120. 

140. 

3D — 

32 £ 

Q 

20 

•00098 

•00105 

•00114 

■00121 

•00125 

•00128 

•00130 

5-04 

•308 

•331 -358 

•379 

•393 

•403 

•409 

20 

25 

•00(197 

■00I04 

•00112 

•00119 

•00123 

•00126 

•00128 

564 

•304 

•328 -353 

•373 

■388 

■397 

•403 

25 

30 

•00095 

•00102 

•00110 

•00116 

•00121 

•00124 

•00126 

64 9 

•300 

■320 346 

•366 

•382 

•390 

•396 

30 

35 

■ . . 

•00100 

•00108 

•00115 

•00120 

•00122 

•00124 

6-67 

•296 

•315 | -341 

•362 

•376 

•385 

•391 

35 

40 

•00093 

•00099 

•00107 

•00114 

•00118 

■(>(>121 

•00123 

7-12 

•292 

•311 337 

•358 

•372 

•381 

•387 

40 

45 

•1 h 11 )92 

•OO098 

•00106 

•00113 

•00117 

•00120 

00122 

7*57 

•288 

•307: -334 

•355 

•369 

•378 

•384 

45 

50 

•00091 

*00096 

•00105 

■00112 

•00116 

•00119 

•00121 

7-97 

■284 

•303 330 

•351 

•366 

■374 

•381 

50 

55 

•O0O90 

•00096 

•00104 

•00111 

00115 

00118 

•00120 

8‘36 

•281 

•301 -327 

•348 

•363 

•371 

•378 

55 

60 

•OOOS9 

•00095 

•00103 

•00110 

•00114 

•00117 

•00120 

8*75 

•278 

•298 1 -325 

•345 

•360 

•368 

'376 

60 

65 

•oooss 

•00094 

•00102 

•00108 

•00114 

•00116 

•00119 

9-09 

•276 

•296 -322 

•341 

•357 

"365 

•373 

65 

70 

•0OOS7 

•00094 

■00102 

•00108 

•00113 

•00116 

■00118 

943 

•274 

■294 -320 

•339 

■355 

•364 

•371 

70 

75 

•00087 

•00093 

•00101 

•00107 

•00112 

•00115 

•00117 

9-77 

•272 

•292 j -318 

•337 

•353 

•362 

•369 

75 

80 

•00086 

•00093 

•00100 

•00107 

■00111 

■00114 

•(>0117 

10-10 

•270 

■291 -315 

•335 

•350 

•360 

•367 

80 

85 

■IK II is.', 

•00092 

•00100 

•00106 

•00111 

•00114 

•00116 

10-40 

•268 

•289 ! '313 

•334 

•348 

■359 

•365 

85 

00 

•00085 

•00091 

•00099 

•00106 

•00110 

■00113 

•00116 

10-70 

'266 

•287 : -311 

•332 

•346 

•357 

•364 

90 

95 

•.. 1 

■in 11 i:h 

•00099 

•00105 

•00109 

•00113 

00115 

1 TOO 

•264 

•286 310 

•330 

■344 

*355 

•362 

95 

100 

•III 11183 

•00090 

•00098 

•00104 

•00109 

•00112 

■00114 

11-30 

•262 

•284 -308 

•327 

•342 

•353 

•360 

100 

110 

•00083 

■.90 

■00097 

•00103 

•00108 

•00112 

•00114 

1T80 

•260 

•282 -306 

*325 

•340 

•351 

•358 

no 

120 

•00082 

•00089 

•00096 

•00102 

•00107 

•001 ! 1 

•00113 

12-40 

•258 

•279 1 303 

•321 

•337 

•349 

*356 

120 

130 

•00081 

•00088 

•00096 

*00101 

*00106 

•00110 

•00113 

12-90 

•256 

•276 '301 

■319 

•333 

•347 

■354 

130 

140 

•0( >08] 

•00087 

•00095 

•00101 

•00105 

•00110 

•00112 

13*40 

•255 

•274 -299 

•317 

•331 

•345 

•352 

140 

150 

•00080 

•00087 

•00091 

*00100 

•00104 

•00109 

•00112 

13-80 

•253 

•272 1 -297 

•315 

•329 

•343 

•351 j 

150 

160 

•00080 

■00086 

•00094 

•00100 

•00104 

•00108 

•00111 

14-30 

•252 

•271 295 

•313 

•327 

•341 

•349 

160 

170 

•00080 

•0(1086 

•00093 

•(» )099 

•00103 

•00108 

•00111 

14-70 

•251 

•270 i -294 

•311 

•325 

•339 

•348 

170 

180 

•00079 

•00086 

•00093 

•00099 

•00103 

•00107 

•00110 

15-10 

•250 

•269 -293 

•310 

•324 

•338 

•347 

180 

190 

•00079 

•OOOS5 

•00093 

•00098 

•00103 

•(>(>[(>7 

•00110 

15-60 

•249 

•268 -292 

•309 

•323 

•337 

•346 

190 

200 

•00079 

•.. 

•00092 

•00098 

•00102 

•00107 

•00110 

16-00 

•248 

.267 -291 

•308 

•322 

•336 

•345 

200 


The values in the above table also give the inductance and reactance per kilometre of each 
conductor for single-phase lines. 

For three-phase lines, where the three conductors are arranged equispaced in one straight line, the 
calculations must be made on the basis of the distance between adjacent conductors for two-thirds 
of the length of the line, and on the basis of twice this distance for the remaining one-third of the 
length of the line. 

167 



























































































ELECTRIC RAILWAY ENGINEERING 

Table LYI. 

Capacities and Charging Currents of Copper Conductors. 


Cross-section of Conductor 
in Square Millimetres. 

Capacity in Microfarads per Kilometre in a Three- 
phase Transmission Line when the Conductors 
are arranged at the Three Corners of an Equilateral 
Triangle. 

Distance between Centres of any Two Conductors 
in Centimetres. 

Diameter of Conductor in 

Millimetres. 

Charging Current in Amperes at 50 Cycles per 
Second in each of the Three Conductors on a 
Tnree-phase Transmission Line, per Kilometre of 
Length of Line, when the Conductors are arranged 
at the Three Corners of an Equilateral Triangle 
•10000 R.M.S. Volts between any Two Conductors. 

Distance between Centres of any Two Conductors 
in Centimetres. 

Cross-section of Conductor 

in Square Millimetres. 

30. 

40. 1 60. 

SO. 

100. 

120. 

140. 

30 

40. 

60. 

80. 

100 . 

120. 

140. 

20 

•0117 

•0108 l -0100 

■0095 

•0092 

■0089 

•0OS8 

5-04 

•0212 

•0196 

•0181 

•0172 

•0167 

•0162 

•0160 

! 20 

25 

•0119 

•0112 1 '0102 

•0097 

•0094 

•0091 

■0089 

5’64 

■0216 

■0204 

■0185 

•0176 

•0171 

•0165 

•0162 

| 25 

30 

0121 

•0114 -0104 

■0098 

■0095 

■0092 

•0090 

6-19 

•0220 

■0207 

•0189 

•0178 

•0172 

0167 

•0163 

30 

85 

0123 

•0116 -0106 

•0100 

•0097 

•0093 

•0091 

6-67 

•0223 

•0210 

•0192 

■0181 

•0176 

•0169 

•0165 

35 

40 

•0125 

•0117 -0108 

•0101 

•0098 

•0094 

•0092 

7-12 

•0227 

•0212 

•0196 

•0183 

■0178 

■0171 

•0167 

40 

45 

•0126 

•0119 0109 

•0103 

•0098 

•0095 

•0093 

7*75 

0229 

•0216 

•0198 

•0187 

•0178 

•0172 

•0169 

45 

50 

0128 

•0120 -0110 

•0104 

•0099 

•0096 

•0094 

797 

•0232 

•0218 

•0200 

•0189 

•0180 

•0174 

■i)171 

50 

55 

•0129 

•0121 -0111 

•0105 

•0100 

•0097 

•0095 

8'36 

•0234 

•0220 

•0202 

•0191 

•0181 

■0176 

•0172 

55 

60 

•0131 

•0122 ! -0112 

•0106 

•0101 

•0098 

•0096 

8-75 

•0238 

•0222 

•0204 

•0192 

•0183 

•0178 

0174 

60 

65 

•0132 

•0123 i -0113 

•0107 

•0102 

■in )99 

•0097 

9-09 

•0240 

•0223 

•0205 

•0194 

•0185 

•0180 

•0176 

65 

70 

•0133 

•0124 -0114 

•0108 

0103 

•0100 

•0097 

9-43 

•0242 

•0225 

•0207 

•0196 

•0187 

•0181 

*0176 

70 

75 

•0134 

•0125 I -0115 

•0109 

•0104 

•0101 

•0098 

9-77 

•0244 

•0227 

•11204 

•0198 

•0189 

•0183 

•0178 

75 . 

80 

■0135 

•0126 ! -0115 

•0109 

•0104 

•0101 

•0099 

10-1 

•0245 

•0229 

•0209 

•0198 

■0189 

•0183 

•0180 

80 

85 

•01.36 

•0127 1 -0116 

•0110 

■0105 

•0102 

•0099 

10-4 

•0247 

■0230 

■0210 

•0200 

0191 

•0185 

•0180 

85 

90 

, -0137 

■0127 -0117 

•0111 

•0106 

■0102 

•0100 

10-7 

•0249 

•0230 

i )212 

•0202 

•0192 

•0185 

•0181 

90 

95 

•0138 

•0128 ’0118 

•0111 

•0106 

•0103 

•0101 

11-0 

•0250 

•0232 

•0214 

•0202 

•0192 

•0187 

•0183 

95 

100 

0139 

•0129 -0119 

•0112 

•tU07 

•0104 

•0102 

11-3 

•0252 

•0234 

•0216 

•0204 

•0194 

•0189 

•0185 

100 

110 

0140 

■0130 -0119 

■0113 

•0108 

■0105 

•0103 

11*8 

•0254 

•0236 

0216 

•0205 

•0196 

•0191 

•0187 

110 

120 

0142 

•0131 1 -0120 

•0114 

•0109 

■0106 

•0104 

12-4 

•0258 

•0238 

•0218 

■0207 

•0198 

•0192 

■0189 

120 

130 

•0143 

•0132 '0121 

•0115 

■0110 

•0107 

■0106 

129 

•0260 

■0240 

0220 

•0209 

•1)200 

•0194 

•0191 ! 

130 

140 

0144 

0132 -0122 

•nllti 

•0111 

■nlOS 

■oioii 

134 

0262 

•0240 

•0222 

•0210 

•0202 

■0196 

•0192 

140 

150 

■0145 

•0133 -0123 

•0117 

•0112 

•0109 

•0107 

13-8 

•( >263 

•0242 

•0223 

•0212 

•0204 

•0198 

•0194 

150 

160 

0146 

■0134 -0124 

•0117 

•0113 

•0110 

•0107 

143 

•0265 

•0244 

•0225 

•0212 

•0205 

•0200 

•0194 

160 

170 

0147 

•0135 '0125 

•tills 

•0114 

•0111 

•0108 

147 

•0267 

•0245 

•0227 

•0214 

•0207 

•0202 

•0196 

170 

180 

•0147 

•0135 -0126 

•0119 

’0115 

•0112 

•0109 

15-1 

•0267 

•0245 

•0229 

•0216 

•0209 

•0204 

•0198 

180 

190 

•0148 

•0136 '0126 

■0120 

•0115 

•0112 

•0110 

15-6 

•0268 

•11247 

•0229 

•0218 

■0209 

•0204 

•0200 

190 

200 

0149 

•0137 ! -0127 

•0121 

•0116 

•0113 

•0111 

16-0 

•0270 

0249 

•0230 

•i )22< i 

•0210 

•0205 

•0202 

200 


The capacities given above are the capacities 
between one wire and neutral point (i.e., point 
of zero potential). For single phase the dis¬ 
tance to neutral point is only - 866 as great 
for a given distance between conductors, and 
hence the capacity per conductor is slightly 
greater. 

The capacity for any relative arrangement 
of the wires will not differ greatly from the 
values above given. 


For a single-phase transmission line, for 
a given distance between conductors, the 
charging current is slightty greater than for 
a three-phase transmission line, per kilometre 
of length of line, at a given periodicity and a 
given voltage between conductors and a given 
diameter of conductor. 


The influence of the earth on the capacity of aerial lines may generally be neglected. 


Hence resistance per conductor = 22*9 ohms. 

Hence reactance per conductor = 35*3 ohms. 

Charging current for conductor at 40,000 volts = 4 X 100 X 0*0189 = 7*55 
amperes. 

Total full load current per phase for0'9P.F. of delivered energy = X 0*9 = 

231,000 

145 amperes. 

Energy component of full load current = 130 amperes. 

Wattless component of full load current = 63 amperes. 

168 







































































THE HIGH TENSION TRANSMISSION SYSTEM 

Combined reactance voltage of step-up and step-down transformers = 006 
23,100 = 1,390 volts. 

^ , 1390 

Reactance = = 10’7 ohms. 

Reactance of line plus transformers = 35’3 + 10*7 = 46'0 ohms. 

A oltage required for sending charging current through line resistance = 

22*9 = 86-5 = be. 


X 


X 


oltage required for sending charging current through reactance = x 46‘0 
= 174 = c d. 

Voltage required for sending energy current through line resistance = 130 X 
22-9 = 2,980 = d e. 

Voltage required for sending energy current through reactance = 130 X 46'0 = 

6,000 = ef. 

\oltage required for sending lagging wattless components through line resistance 
= 63 X 22-9 = 1,440 — f g. 

\ oltage required for sending lagging wattless component through reactance = 63 
X 46-0 = 2,900 = g h. 

These are plotted in the following diagram :— 



and from the relative lengths of the lines a h and a b the necessary voltage at the 
generating end is found to be 29,100. 

For unity power factor of the delivered energy, the components / g and g h 
become zero, and the diagram becomes as follows:— 



the voltage at the generating end being but 26,600, for obtaining 23,100 at the 
receiving end. 

In the next diagram the P.F. is taken at 0'95. For this value the wattless com¬ 
ponent of the load current is 45'o amperes. 

Hence /g = 45-5 X 22*9 = 1,040 volts. 
g h — 45‘5 X 46'0 = 2,090 volts. 



169 


6 














ELECTRIC RAILWAY ENGINEERING 


The diagram for P.F. = 0 - 8 is next given :— 

f g = 87 X 22’9 = 1,990 volts. 
g h = 87 X 46'0 = 4,000 volts. 



For a power factor of 0‘6, the wattless component of the received current is 

115 amperes. , ~ _ _ „,_ 

1 fg — 115 X 22’9 = 2,640 volts. 

g h = 115 X 46 0 = 5,800 volts. 



In the curve in Fig. 145 there are plotted 
against the power factors the voltages required 
at the generating end of the line in order to 
maintain a constant voltage of 28,100 volts per 
phase (40,000 volts between lines) at the 
receiving end of the line. 

The writers arrived at the method above 
described while endeavouring to simplify and 



Fig. 145. Curve showing Voltage required at 
Generator for 23,100 Volts per Phase at 
Receiving End with Different Power Factors. 

170 



Fig. 145a. New York Central Rail¬ 
way : Plan, Elevation, and Sections 
of Pole for Transmission Lines. 

















































































THE HIGH TENSION TRANSMISSION SYSTEM 


to render more useful for every-day work the methods described by Perrine and 
Baum in their paper read before the American Institute of Electrical Engineers on 
May 18th, 1905, and can, therefore, only claim originality with respect to the more 
general applicability and simplicity which they believe has been attained. 

Fig. 145 a is a drawing of a typical steel tower for supporting overhead high 
tension transmission lines. This tower is the standard employed by the New York 
Central Railway for the overhead portion of their transmission line. The tower 
is of latticed steel structure set in a bed of concrete. The cross arms are of yellow 
pine and the conductors spaced 36 inches apart. The poles are spaced 150 ft. apart 
on the straight and closer on curves, according to the radius. The insulators are 
mounted on steel pins. The transmission is at a pressure of 11,000 volts. 


Chapter VII 


THE SUB-STATIONS 


OB railways employing alternating current motors on the cars, the sub-stations, 



X where employed, are equipped with stationary (or static) transformers, i.e., with 
voltage-transforming apparatus not comprising any rotating parts. Where the 
voltage employed at the generating station for such railways is sufficiently low, the 
sub-stations are sometimes dispensed with altogether, and the voltage is transformed 
to the still lower value required by the motors, by means of transforming apparatus 
carried on the car or train. Indeed, in the course of the Berlin-Zossen tests, a loco¬ 
motive was tested equipped with polyphase motors wound for a pressure of 10,000 volts, 
enabling voltage-transforming apparatus to be dispensed with altogether. As we shall 
see in a subsequent chapter, the single phase commutator motor, as at present developed, 
requires a rather low pressure at its terminals; hence transforming apparatus is 
employed on the car or train, in order to reduce the voltage on the rail or trolley from 
the customary 3,000 to 6,000 volts or higher, to some 250 volts at the motors. 

All further allusions to alternating current systems, so far as relates to sub-stations, 
will, however, be reserved for the sections dealing with these systems in subsequent 
chapters. 

In the present chapter we shall discuss the sub-station as employed in the three- 
phase, continuous-current system at present so extensively employed in electric traction. 

As regards the equipment of sub-stations of this class, there arises the question 
of the type of transforming apparatus to be employed. We have the choice of two 
thoroughly reliable types. In the first the voltage is reduced from that of the high 
tension transmission line to a low voltage, by ordinary step-down stationary transformers. 
These step-down transformers are generally either of the air blast or of the oil-immersed, 
water-cooled type. In some cases, instead of the latter type, oil-cooled transformers 
are employed, the water-cooling system being dispensed with. 

The low voltage current from the secondaries of the step-down transformers 
is next led through potential regulators to the alternating current side of rotary 
converters. These rotary converters may be either of the quarter-phase, three-phase, 
or six-phase type. Six-phase rotary converters are now almost invariably emplo} 7 ed. 
The great advantages which six-phase rotaries possess over three-phase rotaries 
have been known for a number of years, 1 but the earlier roads had been equipped 
with three-phase rotaries, and it is only very recently that the conservatism and 
inertia which led to a continuance of their use has been largely overcome. Most 
new undertakings are using or arranging to use six-phase rotaries. 

From the commutator (continuous-current) side of the rotary converters, the 
current, generally at from 550 to 650 volts, is led to the conductor rail or trolley. 

1 See the authors’ treatise on “ Electric Machine Design,” Part III. (. Engineering , 1906). 


172 


THE SUB-STATIONS 


There are many points in favour of the alternative plan of substituting motor- 
generators for the above-described system of step-down transformers, potential 
regulators, and rotary converters. 

Alien motor-generators are used, the current is supplied at the voltage of the 
high tension transmission line direct to the terminals of a synchronous motor 
which is direct-connected to a continuous-current generator which supplies current 
at from 550 to 650 volts to the conductor rail or trolley. Generally, as above 
stated, the current is supplied to a synchronous motor without the interposition of 
step-down transformers. Where, however, the voltage employed on the high 
tension transmission line is greater than 12,000 volts, step-down transformers are 
generally employed. It is also highly probable that induction motors will be 
employed to a greater extent in future for driving the continuous-current generators. 
Where some of the motor-generator sets employ synchronous motors, and others 
employ induction motors, the lagging current of the latter may be offset by over¬ 
exciting the synchronous motors and thus causing them to absorb a leading current, 
so that the resultant current from the generating station and in the high tension 
transmission line may be in phase with the voltage. In like manner the resultant 
current may be adjusted to lead the voltage in phase, and this will occasion a rise 
of voltage on the transmission line if the over-excitation and the line inductance 
be sufficient, and will, with less over-excitation or line inductance, tend to partly 
offset the I.E. drop on the line. 

Not only may we thus, in a system employing motor generators at the sub-station, 
very readily control the voltage, but even when such voltage control is inexpedient the 
continuous-current voltage supplied by the generator member of the motor-generator 
set will be altogether independent of variations in the alternating current voltage. 

This continuous-current generator will be in all respects the equivalent of a 
continuous-current generator direct-connected to an engine with the same 
percentage speed regulation as that of the large steam engines at the generating 
station. The sub-station continuous-current generator may be shunt-wound, or it 
may be compounded for constant terminal voltage at all loads, or for a voltage 
increasing with the load. The amount of loss in the high tension transmission- 
line has no influence upon its operation. One may, and, in long distance transmission, 
must, from economical considerations, have 20 per cent, voltage drop, or even 
higher, in the high-tension line, and yet may have just as perfect voltage regulation 
at the commutator of the continuous-current generator as could be obtained with 
5 per cent, drop or less. Thus, in a case where motor generators are employed, 
one will expend just so much for transmission cables as to obtain maximum economy 
when estimated on the basis of the interest on this capital outlay for cables and the 
cost of producing the energy dissipated in the transmission line. But when rotary 
converters are used, it becomes practically impossible to obtain satisfactory automatic 
control of the commutator voltage with more than 5 per cent, to 10 per cent, 
resistance drop in the high-tension line, and a thoroughly excellent result is only 
to be obtained by a very low resistance drop. Hence a successful plant with rotary 
converters in the sub-stations, only becomes economically possible where the 
length of transmission is not great, or where, in order to obtain a sufficiently low 
line drop, a higher voltage is employed for transmission than would be required for 
the operation of motor generators. These considerations have general^ not been 
sufficiently emphasised in comparing the two systems. They corroborate the 
generally accepted view that the use of rotary converters is attended with higher 

173 


ELECTRIC RAILWAY ENGINEERING 


efficiency in operation than is the case where motor generators are used. But they 
are at variance with another generally accepted conclusion, namely, that a lesser 
first cost may be attained by the use of rotary converters. This may often be 
the case for short distances, but for other conditions the greatly increased outlay 
necessary for cables will generally lead to the opposite result. The question resolves 
itself for any given case, into comparing the slightly greater interest on capital 
expenditure when rotary converters are used, against the cost of operation with 
motor generators. For conditions where this comparison shows little to choose 
between the two systems, motor generators should be employed on the score of their 
great superiority in convenience of operation. 

In order to demonstrate the soundness of this position, the properties of these two 
types of apparatus will be examined. 1 



Fig. 146. Fig. 147. Fig. 148. 

Figs. 146, 147, and 148. Phase Characteristics of Hypothetical Synchronous Motors. 

Consider the case of a hypothetical synchronous motor and transmission system 
for which the following assumptions would hold :— 

(1) No reactance in armature; 

(2) No resistance in armature; 

(3) Constant voltage at collector rings. 

The phase characteristics of such a motor would resemble the curves of Fig. 146, 
where a given constant field excitation corresponds to minimum current input for all 
loads, i.e., to unity power factor for all loads. 

Suppose next that assumptions 2 and 3 still hold good, but that the armature has 
reactance. In proportion to the magnitude of this reactance the curve of field 
excitation for unity power factor will bend toward the right, as shown in Fig. 147. 

Should, on the other hand, assumptions 1 and 3 hold good, but should allowance 
require to be made for the resistance of the armature windings, Fig. 146 would be 
modified in the manner shown in Fig. 148, the curve of field excitation for unity power 
factor sloping to the left. 

If instead of the third assumption, to the effect that there is constant voltage at 
the armature terminals of the synchronous motor, there is a drop of voltage in the 
line proportional to the load on the motor, the curve will be modified in the same way 
as by resistance drop in the armature, and the slope to the left will be greater the 
greater the line drop. If the arrangements should be such that the terminal voltage 
increases with the load, the effect would be to reduce the slope to the left occasioned by 

1 Most of the material on pp. 174 to 188 is reproduced with the kind permission of the Electrical 
Revietv , from an article by one of the authors, and entitled “ Motor Generators and Rotary Con¬ 
verters,” Yol. LIII., pp. 519—521, pp. 528—529, pp. 607—609, and pp. 647—650. 

174 
























































THE SUB-STATIONS 


the armature resistance, or, with sufficient rise in terminal voltage, to bring the line hack 
to the vertical, or even to swing it over to a slope to the right. Now, when a continuous- 
current generator is directly driven from such a synchronous motor, the commutator 
voltage, according to the method and adjustment of the excitation, may automatically 
deciease, remain constant, or increase with the load, and this source may be employed 
for the excitation of the synchronous motor. The net result from these considerations is 
that we may readily arrange, if necessary, by series coils in addition to shunt coils, 1 for 
a synchronous motor to be automatically excited with held currents suitable to secure 
practically unity power factor at all loads. This is the condition for a minimum loss of 
energy in the high tension transmission line, and for a minimum outlay for copper. 

We may illustrate this by a practical case. Let a three-phase synchronous motor 
be direct-connected to a continuous current generator of 800-K.W. rated output, com¬ 
pounded for a terminal voltage of 500 volts at no load, and 525 volts at full load. At 
89 per cent, combined efficiency for the set, the synchronous motor will absorb 

= 900 K.W. at full load. 

Uoy 

The motor has an external stationary armature with Y-connected windings, fed 
over a three-core cable direct from the central station, no other apparatus being 
supplied from this cable. The central station voltage is maintained constant at 5,800 
volts, and at full load of the synchronous motor at unity power factor, the drop in 
transmission line plus armature resistance is 10 per cent, per phase, the voltage at 
the motor (considering the armature resistance to be transferred and added to the line) 
thus falling from 5,800 volts at no load to 

5,800 x *90 = 5,200 volts 

at full load. 

The voltage per phase in the armature is 

= 3,850 volts at no load, 


and = 3,000 volts at full load. 

The current per phase is thus 

--- , = 100 amperes at full load. 

3 x 3,000 1 

Let the slots and windings of the synchronous motor be so proportioned that at 
100 amperes the reactance voltage per phase is 1,000 volts, and let the combined 
armature strength of the three phases amount to 4,200 maximum ampere turns per 
pole. Let the field excitation required for 5,800 terminal volts at no load, equal 7,000 
ampere turns per pole. 

The first step is to find the field excitation corresponding to 100 amperes per 
phase at unity power factor and 5,200 terminal volts. 

We will take into account the saturation by estimating the no load ampere turns 
for 5,200 terminal volts, at 

5 200 

0'96 X T800 X T000 = 6,000 ampere turns. 

The armature demagnetisation, at 100 amperes and unity power factor, amounts to 
sin ^ tan ~ ^’qqq ^ X 4,200 = 0*32 X 4,200 = 1,350 ampere turns. 


1 In eases where a compound-wound synchronous motor would be required, the armature 
would have to be of the internal revolving type. 


175 







ELECTRIC RAILWAY ENGINEERING 


Hence at full load of 100 amperes input, and 5,200 terminal volts, the excitation 
required for unity power factor would be 

6,000 + 1,350 = 7,350 ampere turns; 

and to obtain approximately unity power factor from no load to full load, the field 
excitation should automatically increase from 7,000 to 7,350 ampere turns per pole, 
that is, by 5 per cent. 

This corresponds to the over-compounding provided for the direct-connected 
continuous-current generator (500 volts at no load up to 525 volts at full load); hence 
the excitation of the synchronous motor may be provided from that source, and an 
automatic control of the power factor at approximately unity, will be obtained for all 

loads. Of course it is by no means necessary 
to obtain so close an agreement, since a very 
considerable deviation from the correct excita¬ 
tion will not occasion more than 1 or 2 per cent, 
deviation from unity power factor. It is evident 
that by designing a synchronous motor with suit¬ 
able armature inductance, armature strength, 
resistance, and degree of saturation, it may be 
arranged for automatic operation at practically 
unity pow r er factor for any reasonable value 
of line drop and of over-compounding of the 
continuous current generator which it drives. 

Although the constants of the synchronous 
motor used for illustrating this explanation 
were chosen at random and are in no sense put 
forward as representing an ideal or even care¬ 
fully considered design, it may be of interest to 
plot its estimated phase characteristics when 
operated under the conditions set forth. These 
are given in Fig. 149 for no load, half-load, 
and full load. The curve passing through the 
minimum points corresponds to unity power 
factor, but excitations corresponding to any 
part of the shaded area shown will give at least 0‘99 power factors, thus permitting 
at full load a total range of variation of the excitation of about 20 per cent., so that it 
would not be worth while to modify the design of the synchronous motor for the sake 
of obtaining better conditions in this respect, even for very different line constants, 
or requirements as to over-compounding of the continuous current generator. 

The characteristic curves of Fig. 149 were estimated on the basis of the armature’s 
magneto-motive force being equivalent to that of the field spools in the proportion of 
1 root-mean-square ampere turn per pole per phase, 
representing a resultant armature strength per pole capable of replacing 
1 X \/2 X 2 = 2*83 ampere turns per field spool, 
this being a proportion experimentally verified by an analysis of a number of three- 
phase machines of a wide range of designs. 

It should not be necessary to follow up this investigation any further so far as 
concerns demonstrating that, with any line loss that could be economically permitted, 
synchronous motors with automatic control for high power factor may be satisfactorily 
employed to drive continuous current generators, which latter, with any range of 

176 









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CAUHc 

Power 


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Field excitation in Ampere Turns per Spool 

149. Phase Characteristics of 
Synchronous Motor for 900 - k.w. 
Input at Rated Load. 





























THE SUB-STATIONS 


compounding within customary requirements, may serve as supply for the synchronous 
motor’s field excitation. 

It will now be demonstrated that with rotary converters, a very different state of 
affairs exists in this respect. 

An analysis of the observed no-load phase characteristic curves of a number of 
three-phase rotary converters of a wide range of ratings with respect to the outputs, 
speeds, periodicities, and voltages, yielded as an average result for estimating the 
effectiveness of the armature magneto-motive for replacing the field magneto-motive 
force the following rule:— 

“When in a rotary converter the magneto-motive force is derived from the armature 
winding itself, in virtue of the wattless component of the alternating current entering the 
armature, a root-mean-square (R.M.S.) value of the armature ampere turns per pole-piece 
per phase, represented by l'OO, equals in effectiveness a field excitation of 2‘15.” 

The expression “six-phase rotary converter” is slightly misleading. It would be 
better described as a three-phase machine with six slip-rings. For the purpose of this 
discussion it is immaterial whether it is distinctly kept in mind that the machine has 
six rings, and it will be convenient to denote by Y current the current equivalent to 
one branch of the Y in a Y-connected synchronous motor of the same capacity and 
voltage. 1 Similarly, by Y voltage will be denoted the voltage from the common 
connection to any one terminal of such an equivalent synchronous motor. 

The arrangement of the armature slots and windings, and the general proportions of a 
rotary converter, are such that it has a comparatively small reactance, and in the following 
investigation the effect of the reactance has been neglected in the interests of simplifying 
the necessarily very tedious work. The conclusions are not thereby appreciably affected. 

A little consideration will suffice to show that so far, as relates to obtaining satis¬ 
factory automatic regulation of the commutator voltage by means of phase regulation, 
there should he employed a comparatively weak armature expressed in armature 
ampere turns per pole, low saturation, and low armature resistance. These conditions 
lead to much more liberally proportioned rotary converters than would otherwise be 
necessary. But in order not to make out too unfavourable a case for the rotary con¬ 
verter, from the standpoint of regulation by phase control, the estimations have been 
based upon a machine with these features, and therefore of decidedly liberal proportions. 

In Table LVII. are set forth the data assumed for the rotary converter : — 


Table LYII. 


Data of 600-7Y.IF. liotary Converter. 


Rated output ...... 

Commutator voltage .... 

Number of poles . ... . 

Periodicity in cycles per second 
Speed in revolutions per minute 
Internal voltage at full load output 
Full load current ..... 

Full load efficiency at unity power factor 


Y voltage 


600 X 0-615 
1-78 


600 K.W. 

600 volts. 

12 . 

25. 

250. 

613 volts. 

1,000 ampe-es. 
96 %. 

213. 


1 In the case of a rotary converter with three slip rings, this is the current per slip ring ; for the 
case of six slip rings it is twice the current per slip ring. In both cases, the alternating current 
component of the total current per armature conductor, is equal to this Y-current divided by v3 and 
by the number of pairs of poles for a multiple-circuit single winding, or by 2, independently of the 
number of poles, for a two-circuit single winding. 

E.R.E. 177 


N 





ELECTRIC RAILWAY ENGINEERING 


At unity power factor the Y amperes input are equal to 

600,000 


0*96 x 8 x 213 


= 980 amperes. 


The armature winding is of the twelve-circuit single type. 

The alternating current component of the resultant current per armature conductor, 
at full load and unity power factor, is equal to 

980 

-i- Q tt = 94’0 amperes. 

1 ' I o X o 

The assumed saturation curve for this machine is given in Fig. 150. This shows 

for 613 internal volts 8,900 ampere turns per field 
spool, and for 600 volts 8,600 ampere turns. 

Hence the ordinates of the full load charac¬ 
teristic for the point of minimum current (unity 
power factor) are 

980 amperes and 8,900 ampere turns. 

The machine has 60 segments and 60 turns per 
pole, consequently 20 turns per pole per phase. To 
replace 8,900 ampere turns per field spool, the 
armature current required is 
8,900 

2H5 X 20 = ^8 amperes per armature conductor. 

This corresponds to a total wattless current 
input of 

208 

94’0 X ^9 = 2,170 amperes per phase. 

Hence for zero field excitation and full load output the total current input is 
equal to 

\7980- + 2,170“ = 2,380 amperes. 



Fig. 150. Saturation Curve of 
a 600-k.w. Eotary Converter. 


By determining in a similar manner the armature current required to replace, 
not the uliolc excitation, as in the above example, but portions thereof, the values in 
Table LVIII. have been derived :— 


Table LYIII . 

Amperes Input to Rotary Converter with Varying Field Excitation, at Full Load Output. 


Voltage at 
Commutator. 

Amperes Output 
from Commutator. 

Field Excitation in 
Ampere Turns. 

Y Amperes Input 
per Phase. 

600 

1,000 

0 

2,380 

600 

1,000 

3,000 

1,760 

600 

1,000 

6,000 

1,200 

600 

1,000 

8,900 

980 

600 

1,000 

11,900 

1,200 

600 

1,000 

14,900 

1,760 

600 

1,000 

17,900 

2,380 


178 


































THE SUB-STATIONS 


Calculations at other loads give the results in Table LIX. for the amperes input 
per phase at varying excitation:— 


Table LIX. 

Amperes Input to Rotary Converter with Varying Field Excitation for various Outputs. 


Ampere Turns Field Exc. for Following Continuous-current Outputs. Y Amperes Input. 


0 

Amperes. 

CO 

V 

g 8 

04 

CO 

CD 

o 5 

iO P yp 

< 

750 

Amperes. 

1,000 

Amperes. 

1,250 

Amperes. 

1,500 

Amperes. 

1,750 

Amperes. 

0 Ampeies 

Output from 

Commutator. 

250 Amperes 

Output from 

Commutator. 

500 Amperes 

Output from 

Commutator. 

750 Amperes 

Output irom 

Commutator. 

cn 

a; <-L 

= o 
32 p 

£ — 

< g = 

lei 

1,250 Amperes 

Output from 

Commutator. 

] ,500 Amperes 

Output from 

Commutator. 

1,750 Amperes 

Output from 

Commutator. 

0 

0 

0 

0 

0 

0 

0 

0 

2.140 

2,180 

2,240 

2.290 

2,380 

2,540 

2,690 

2,860 

3,000 

3,000 

3,000 

3,000 

3,000 

3,000 

3,000 

3,000 

1,400 

1,440 

1,520 

1.628 

1,760 

1.920 

2,090 

2,300 

6,000 

6,000 

6,000 

6.000 

6,000 

6,000 

6,000 

6,000 

650 

720 

820 

1,010 

1.200 

1,390 

1.630 

1,880 

8,600 

8,690 

8,780 

8,870 

8,900 

9,040 

9,130 

9,210 

40 

255 

485 

715 

980 

1,190 

1,435 

1,700 

11,200 

11,380 

11,560 

11.740 

11.900 

12.080 

12,260 

12,420 

650 

720 

820 

1,010 

1,200 

1.390 

1.630 

1,880 

14,200 

14,380 

14,560 

14,740 

14,900 

15,080 

15,260 

15,420 

1,400 

1,440 

1,520 

1,628 

1,760 

1,920 

2,090 

2,300 

17,200 

17,380 

17,560 

17,740 

17,900 

18,080 

18,260 

18,420 

2,140 

2,180 

2,240 

2,290 

2,380 

2,540 

2,690 

2,860 


These values are plotted in the curves of Fig. 151. The points at which the broken 
line a, b intersects the various load charac¬ 
teristics, correspond to the values of the total 
excitation automatically obtained when the 
shunt winding is adjusted to supply a 
constant excitation of 6,000 ampere turns, 
and the series winding to give 3,850 ampere- 
turns at the full load output of 1,000 
amperes, this being 64 per cent, compounding 
at full load. This adjustment corresponds 
to unity power factor at three-quarter load. 

The excitations at the different loads for the 
machine thus adjusted are given in Table LX. 


ctj SOD 
-c: 
cl 


Table LX. 

Adjustment with 64 per cent. Compounding at 
Full Load, and for Unity Power Factor at 
75 per cent, of Full Load. 


Q. ooo 
£ 

^ 800 


Per cent, of 
Full Load. 

o 

25 per cent. 
50 ,, 

75 

100 „ 

125 

150 ,, 

175 


Total Excitation in Ampere 
Turns per Pole. 
6,000 
6,960 
7,920 
8,870 
9,830 
10,790 
11,750 
12,700 


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0 2000 4000 6000 8000 10000 12000 14000 16000 18000 

Field excitation in Ampere-Turns per pole. 

151. Curves showing Amperes Input 


© 

per Phase at various Loads 
600-k.w. Rotary Converter. 


of A 


In Table LXI. are given the corresponding total amperes input per phase, the 
energy component, and the wattless component, together with the efficiency and the 
power factor at all loads. 


179 


N 2 











































































ELECTRIC RAILWAY ENGINEERING 

Table LXI. 

Rotary Converter adjusted for Unity Power Factor at Three-quarter Load and 64 per cent. 

Compounding at Full Load. 


Per cent, of Full 
Load Amperes 
Output from 
Commutator. 

Commercial 
Efficiency of 
Rotary 
Converter. 

Y Amperes 
Input to Rotary 
Converter 
per Phase. 

Energy 
Component of 
Amperes Input. 

Wattless 
Component of 
Amperes Input. 

Power Factor. 

Field 

Excitation 
(Ampere Turns 
per Spool). 

0 % 

0 % 

640 

25 

640 

0-039 

6.000 

25 % 

88-0 % 

495 

255 

425 

0-515 

6,960 

50 % 

94-2 % 

530 

485 

212 

0-915 

7,915 

75 % 

95-4 % 

720 

720 

0 

1-00 

8,870 

100 % 

96-0 % 

990 

970 

195 

0-980 

9,830 

125 % 

95-4 % 

1,255 

1,190 

400 

0-950 

10,790 

150 % 

94-6 % 

1,570 

1.440 

615 

0-920 

11.750 

175 % 

93-5 % 

1,910 

1,700 

872 

0-890 

12,700 

200 % 

92-0 % 

2,300 

1,980 

1,175 

0-860 

13.650 


The curves in Fig. 152 (facing p. 182) are plotted from the results set forth in 
Table LXI. 

The next step is to investigate the performance of the rotary converter when thus 
adjusted. The rotary converter is to be operated from the secondaries of transformers 
whose primaries are fed over a high tension line. But for convenience of calculation the 
resistances and voltages will be reduced to the equivalent Y voltage of the rotary converter. 

At no load, the Y voltage at the slip-rings of the rotary converter is 


600 X 0-615 
\/"3 


213 volts. 


First assume that in transmission line, step-down transformers, and rotary con¬ 
verters, the equivalent resistance and the equivalent reactance are each equal to 0 01 
ohm per phase. It is required to determine the voltage at the central station in order 
to obtain 600 volts at the commutator at no load. From Fig. 151 the input per phase 
is found to be 640 amperes and is practically wholly wattless. Hence 
Pieactance voltage per phase = 640 x O’Ol = 6‘4 volts. 

Resistance ,, „ „ = 640 x O'Ol = 6'4 ,, 

Constructing the diagram in Fig. 153, the “equivalent” voltage at the generating 
end of the line is found to be equal to 219'5 volts. 

.'. At 219'5 volts at the generating end of the line, the no load commutator volt¬ 
age is equal to 600 volts. 

In Fig. 154 is given the corresponding diagram for half-load, the potential at the 
generating end being maintained constant at the value of 219’5 volts derived at no 
load. From the phase characteristic at half-load in Fig. 151, the total current input 
per phase is found to be 530 amperes, and the minimum value of the curve, 485 
amperes, is the energy component. Hence the wattless component is equal to 

\/o 30 2 — 485 2 = 212 amperes. 

The four component voltages obtained as the products of these component 
currents with the reactance of 0 - 01 ohm per phase and the resistance of 0*01 ohm per 
phase are— 

485 X 0-01 = 4*85, 

485 X 0-01 = 4*85, 

212 X 0-01 = 2-12, 

212 X 0-01 = 2-12, 

i So 


























THE SUB-STATIONS 


and these are plotted in the diagram of Fig. 154, which shows that the Y voltage of the 
rotary converter has fallen from 213'0 volts to 212'3 volts, so that the commutator 
voltage is 

—— x 600 = 598 volts. 

213-0 

The diagrams in Figs. 155, 156 and 157 have been similarly derived for three- 
quarter load (when the current is in phase), and for 50 per cent, and 100 per cent, 
overloads (at which values the current leads). 

These results are brought together in Table LXII. 


Y-voltage at rotary converter = 213 0 volts. 6 : 4 volts 

——=- 6-4 volts 

Equivalent V- voltage at generating end of line=219-5 volts. 

Fig. 153. 

No Load. 

Equivalent' Y- voltage at generating end of line = 219-5 volts }' vo/ts 

-- -----’ _,£v- 21 volts 

r voltage at rotary converter = 212-3 volts ■ 4 9 voltf 

4'9 volts 

Fig. 154. 

Half Load. 

" Eguivalent " Y- voltage at generating end of line = 219-5 vo/ts. 

v Tl - 1 — -- - volts 

Y voltage at rotary converter = 212-3 volts . Y>. 2 v0/ts 

Fig. 155. 

Three- 

Quarter 

Load. 

*' Equivalent" Y- voltage at qeneratinq end of line = 2/9-5 vo/ts 
-—_--- - --- volts 

YEEETTl ---_ '~l6-2 volts 

- ^J' 44 V0/tS 

T 14 4 volts 

Fig. 156. 

Fifty 
per Cent. 
Ovtrload. 

Equivalent" Y- voltage at generating end of line = 2/9 5 vo/ts. //fl vo/f< , 

- > volts 

Wav,,t, 

uy ' s vo/ts 

'19-8 volts 

Fig. 157. 

One 

Hundred 
per Cent. 
Overload. 


Figs. 153—157- Diagram for determining Generator Yoltage at various Loads. 


i 8 i 

























ELECTRIC RAILWAY ENGINEERING 

Table LXII. 

Variation in Rotary Converter Voltage with Varying Load. 

Total resistance per phase = 0*01 ohm. 

Total reactance per phase = 0‘01 ohm. 

64 per cent, compounding at full load. 

Adjustment for unity power factor at three-quarter load. 
Equivalent voltage at the generating end of the line = 219‘5 volts. 


Per cent, of 
Full Load. 

0 

25 per cent. 
50 

75 „ 

100 

125 

150 

175 

200 


Y Voltage. 

213-0 

2128 

212-3 


210-4 
209 5 


Commutator 

Voltage. 

600 


598 

598 


592 


589 


In the same way as for 0'01 ohm reactance per phase, values were obtained 
for 0-02, 0*03, and 0-04 ohm reactance per phase, all with (TOl ohm resistance 
per phase. Then followed corresponding sets of calculations with resistances of 
0-02, 0'03, and 0*04 ohm per phase. The results of these calculations are given in 
Table LXIII. 


Table LXIII. 


64 per cent. Compounding at Full Load, Adjustment for Unity Power Factor at 

Three-quarter Load. 







Commutator Voltage. 



Per cent. 









of Full 
Load. 

•01 

•01 

•01 

•01 

•02 

•02 

•02 

•02 

= Olim Resistance. 


■01 

•02 

•03 

•04 

01 

•02 

•03 

•04 

= Ohm Reactance. 

0 

600 

600 

600 

600 

600 

600 

600 

600 


25 % 1 

— 

— 

— 

— 

— 

— 

— 

— 


-50 % 

598 

610 

620 

632 

583 

596 

609 

620 


75 % 

597-5 

615 

631 

645 

576 

594 

610 

626 


100 % 

— 

— 

— 

— 

— 

— 

— 

— 


125 % 

— 

— 

— 

— 

— 

— 

— 

— 


150 % 

592 

621 

650 

676 

547 

578 

605 

628 


175 % 

— 

— 

— 

— 

— 

— 

_ 

_ 


200 % 

589 

629 

665 

710 

527 

564 

599 

627 


Generated 

Voltage. 

219 5 

225*9 

232-2 

238-6 

219-5 

225-9 

232-2 

- 

238-6 



































































Per Cent.of Full Load Current from Commutator 

Eotary Converter with 64 per cent. Compounding. 
Fig. 152. 



Per Cent.of Full Load Current from Commutator 


Rotary Converter with 30 per cent. Compounding. 
Fig. 158. 



Shunt Wound Rotary Converter (j.e ., 0 Compoundin 

Fig. 159. 


Curves of Efficiency and Power Factor of a 600 Iv.W. Rotary Converter. 


Figs. 152, 158, 159. 


Y-Amperes Input per Phase 



































































































































THE SUB-STATIONS 


Table LXIII.— continued. 


1 

Per cent. | 





Commutator Voltage. 




of Full 
Load. 

•03 

■03 

•03 

•03 

•04 

•04 

■04 

•04 

= Ohm Resistance. 


■01 

•02 

•03 

•04 

•01 

•02 

■03 

•04 

= Ohm Reactance. 

0 

600 

600 

600 

600 

600 

600 

600 

600 


25 % 

— 

— 

— 

— 

— 

_ 



50 % 

572 

579 

597 

609 

560 

573 

577 

590 


75 % 

559 

570 

593 

610 

540 

555 

565 

582 


100 % 

— 

— 

— 

_ 

_ 

_ 




125 % 

150 % 

•—- 

— 

— 

_ 

— 

_ 

_ 



507 

531 

565 

586 

465 

493 

510 

534 


175 % 

— 

— 

— 

_ 

_ 

_ 




200 % 

465 

495 

533 

555 

402 

432 

453 

475 


Generated 

Voltage. 

220-0 

224-8 

233-5 

239-5 

220-8 

227-0 

231-0 

237-8 



The results in Table LXIII. are plotted in the row of curves of Fig. 160, the whole 
group comprised in this row corresponding to an adjustment for unity power factor at 
three-quarter load, with 64 per cent, compounding at full load, the total full load 
excitation thus consisting of 

6,000 shunt ampere turns per pole and 
3,830 series ampere turns per pole. 

The Effect of a Change in the Adjustment of the Compounding. 

Suppose the field excitation is so rearranged that it shall at no load give 7,000 
ampere turns, at three-quarter load 8,870 ampere turns, and at full load 9,500 
ampere turns, there thus being 36 per cent, compounding at full load. This adjust¬ 
ment is indicated by the broken line c d in Fig. 151, and corresponds to the values given 
in Table LXIY. for the amperes input per phase at various outputs, the energy com¬ 
ponent, the wattless component, the efficiency and the power factor. 


Table LXIY. 

Rotary Converter adjusted for Unity Power Factor at Three-quarter Load and 

36 per cent. Compounding at Full Load. 


Per cent, of Full 
Load Amperes 
Output from 
Commutator. 

Commercial 
Efficiency of 
Rotary 
Converter. 

Y Amperes 
Input to Rotary 
Converter 
per Phase. 

Energy 
Component of 
Amperes Input. 

Wattless 
Component of 
Amperes Input. 

Power Factor. 

Field 

Excitation 
(Ampere Turns 
per Spool). 

0 

0 % 

380 

25 

380 

0-066 

7,000 

25 % 

88-0 % 

370 

255 

266 

0-680 

7,620 

50 % 

94-3 % 

500 

485 

123 

0-970 

8,250 

75 % 

95-5 % 

720 

720 

0 

1-000 

8,870 

100 % 

96-0 % 

983 

975 

115 

0-991 

9,500 

125 % 

95-5 % 

1,215 

1,190 

244 

0-980 

10,120 

150 % 

94-8 % 

1,490 

1,440 

388 

0-967 

10,750 

175 % 

93-5 % 

1,775 

1,700 

510 

0-957 

11,370 

200 % 

92-0 % 

2.090 

1,980 

665 

0-946 

12,000 


183 






































































ELECTRIC RAILWAY ENGINEERING 


The results in Table LXIY. are plotted in Fig. 158 (facing p. 182). A set of results 
has next been calculated for the performance of the rotary converter with this new 
adjustment, when operated under the same conditions of reactance and resistance as 
when adjusted for 64 per cent, compounding. The results are compiled in Table LXY. 


Table LXV. 

36 per cent. Compounding at Full Load, Adjustment for Unity Power Factor at 

Three-quarter Load. 


Per cent, 
of Full 
Load. 


0 

25 % 
50 % 
75 % 

100 % 
125 % 
150 % 
175 % 
200 % 


Generated 

Voltage. 


Commutator Voltage. 


•01 

•01 

•01 

•01 

•02 

•02 

•02 

•02 

= Ohm Resistance. 

•01 

•02 

•03 

‘04 

■01 

•02 

•03 

•04 

= Ohm Reactance. 

600 

600 

600 

600 

600 

600 

600 

600 


593 

600 

605 

611 

579 

586 

593 

601 


589 

599 

607 

_ 

617 

570 

578 

587 

598 


578 

595 

609 

622 

537 

553 

565 

578 


570 

587 

603 

615 

509 

528 

540 

551 


216-8 

220-6 

224-4 

228-2 

216-8 

220-6 

224-4 

228-2 



Per cent. 

Commutator Voltage. 

of Full 










Load. 

•03 

•03 

•03 

•03 

•04 

•04 

■04 

•04 

= Ohm Resistance. 


•01 

■02 

•03 

•04 

•01 

•02 

•03 

•04 

= Ohm Reactance. 

0 

600 

600 

600 

600 

600 

600 

600 

600 


25 % 

— 

— 

— 

— 

— 

— 

— 

— 


50 % 

565 

572 

580 

586 

553 

560 

566 

575 


75 % 

550 

560 

566 

577 

530 

539 

549 

557 


100 % 

— 

— 

— 

— 

_ 

_ 

_ 

_ 


125 % 

— 

— 

— 

— 

— 

_ 

— 

_ 


150 % 

495 

512 

523 

535 

454 

468 

480 

493 


175 % 

— 

— 

— 

— 

_ 

_ 

— 

_ 


200 % 

451 

469 

480 

487 

392 

406 

416 

423 


Generated 

Voltage. 

216-9 

220-7 

224-5 

228-3 

217-5 

220-9 

224-8 

229-2 



The curves embodying the results of Table LXV. are to be found in the row of 
curves in Fig. 161, entitled “ 36 per cent. Compounding.” 


The Effect of Operating the Rotary Converter with Shunt Excitation alone. 

We shall next investigate the action of this rotary converter when shunt-excited, 
and with 9,000 ampere turns, at full load, this giving unity power factor at full load 
and 980 amperes input per phase. 


184 




































































































THE SUB-STATIONS 


The straight line e /drawn in Fig. 151 through the points 

9,500 — 210 and 
9,000 — 980 

gives, by its points of intersection with the characteristic curves at various loads, the 
values entered in Table LXVI. 


Table LXYI. 

Rotary Converter with Shunt Excitation, 


i.e., with 0 per cent, compounding, and adjusted for unity power factor at full load. 


Per cent, of Full¬ 
load Amperes 
Output from 
Commutator. 

Commercial 
Efficiency of 
Rotary 
Converter. 

Y Amperes 
Input to Rotary 
Converter 
per Phase. 

Energy 
Component of 
Amperes Input. 

Wattless 
Component of 
Amperes Input. 

Power Factor. 

Field 

Excitation 
(Ampere Turns 
per Spool). 

0 

0 % 

210 

25 

208 

0119 

9,500 

^5 % 

88-0 % 

320 

255 

193 

0797 

9,400 

50 % 

94-3 % 

503 

485 

140 

0 965 

9,250 

75 % 

95-5 % 

725 

720 

70 

0994 

9,150 

100 % 

96-0 % 

980 

980 

0 

1000 

9,000 

125 % 

95-5 % 

1,195 

1,190 

80 

0996 

8,800 

150 % 

94-8 % 

1,448 

1,440 

142 

0-995 

8,600 

175 % 

93-5 % 

1,710 

1,700 

200 

0-994 

8,400 

200 % 

92-0 % 

1,995 

1,980 

245 

0-993 

8,200 


The results in Table LXYI. are plotted in the curves in Fig. 159, from which it 
is seen that for the rotary converter with shunt excitation there is practically no 
wattless component available for magnetisation and demagnetisation in regulation. 

For a resistance of 0’01 ohm and a reactance of 0‘01 ohm per phase, and with 
222*6 volts at the generator, the regulation is as follows:— 

No load ..... Commutator voltage = 632 

Full load. ,, „ = 600 

2 x full load .... ,, ,, = 562 

For a resistance of 0*01 ohm and a reactance of 0*04 ohm per phase and a 
generator voltage = 222*6 :— 

No load ..... Commutator voltage = 660 
Full load ..... ,, ,, = 600 

2 X full load .... ,, ,, = 557 

For a resistance of 0'02 ohm per phase, the values set forth in Table LXVII. 
were obtained. 


Table LXVII. 

Shunt Excitation and a Resistance of 0*02 Ohm per Phase. 


Ohm Reactance per Phase 

Generator Voltage .... 

0-01 

232 

0-02 

233 

0-03 

234 

0-04 

235-5 



Commutator Voltage. 


No Load ....... 

663 

678 

696 

725 

Full Load ...... 

600 

600 

600 

600 

1-25 X Full Load ..... 

— 

— 

— 

565 

1*5 X Full Load ..... 

— 

— 

521 

— 

1"75 X Full Load ..... 

546 

527 

— 

“ 


185 




































ELECTRIC RAILWAY ENGINEERING 


The values in Table LXVII. are plotted in the second group of curves of Fig. 162. 

The curves in Fig. 163 summarise the results for “64 per cent, compounding,” 
“36 per cent, compounding,” and for shunt excitation ( i.e ., no compounding ). 

Taking the diagrams of Figs. 160 to 163 in vertical rows, those at the left correspond 
to low line resistance; and the further one goes towards the right the greater is the 
line resistance. The curves of the upper left-hand diagram, where the line resistance 
is low and the compounding high, are in striking contrast to those lower down and 
towards the right, where the line resistance is greater and the compounding lower. 

The results of this investigation, as brought together in the groups of curves of 
Figs. 160 to 163, afford ample evidence that only in cases where the distance of trans¬ 
mission is so short, the voltage so high, or the outlay for cables so great that a very 
low resistance per phase is obtained, can rotary converters be satisfactorily operated 
for automatic control of the commutator voltage for practically constant voltage at all 
loads, much less then for 5 per cent, or 10 per cent, higher commutator voltage at full 
load than at no load. Even with a low resistance per phase, it is necessary to provide 
large, expensive, and wasteful auxiliary reactance coils in order to obtain satisfactory 
voltage control by automatic phase adjustment, and for anything more than a very 
low resistance per phase, there is soon reached a value of the reactance beyond which 
it is ineffective in producing improved conditions in this respect. In fact, with shunt 
excited rotary converters, as may be seen from the curves in Fig. 162, and even with a 
small percentage of series winding, reactance makes the regulation still worse. The 
curves also show the great importance of a large percentage of series winding from 
the standpoint of regulation of the commutator voltage by phase control. 

It must further be remembered that these estimations have been made upon a 
rotary converter of very liberal design. From any other standpoint than that of 
regulation, a much cheaper design would have been permissible, but would, so far as 
relates to this feature of voltage control, have led to decidedly worse results. In 
consequence of the absence of armature reaction in rotary converters operated at unity 
power factor, such a machine should, in the interests of an economical design, be 
proportioned with a strong armature and with a magnetic circuit of small cross- 
section; the saturation should also be high, as also the “nominal ” current density 
in the armature conductors, because of the partial mutual neutralisation of the 
alternating current by the continuous-current components of the total current. All 
these features have, however, to be partly sacrificed in the interests of phase control. 
Then, again, the weaker the series winding, the higher is the average power factor of 
a rotary converter operated in this manner. This may be seen by comparing the 
curves of Figs. 152, 158, and 159. Thus, again, we see that good automatic com¬ 
mutator voltage regulation by phase control requires a poor power factor at all except 
a very narrow range of loads. 

Practical Application of these Principles. 

It should be of interest to apply these principles to a typical case, and as very 
complete data have been published 1 on the Central London Railway, this installation 
may be chosen for our purpose. 

Owing to the short distance of 6 miles from the power-house to the most remote 
sub-station, the conditions are especially favourable to a fair showing for rotary 
conveners. I he original sub-station installation consisted mainly of six 900-kilowatt 

1 See Engineering, February 18th, 25th, and March 4th, 1898; Electrical Revieiv, June 1st, 
8th, 15th, 22nd, and 29th, 1900. 

























































































































































































































































































































































































































































































































































































































































THE SUB-STATIONS 


rotary converters, twenty-one 300-kilowatt air blast transformers, with blower sets for 
circulating the air through them, and all necessary switchgear and auxiliary apparatus. 
1 hese were located in three sub-stations, distant respectively lb, 3£, and 6 miles 
rom the generating station. The average distance is, therefore, about 3| miles. The 
high tension cable equipment for the whole plant comprised 30,500 ft. of lead- 
sheathed, paper-insulated three-core cables of a cross-section of 0-1875 sq. ins. of 
copper per core and 64,000 ft. of lead-sheathed, paper-insulated three-core cables of a 
cross-section of 0 - 125 sq. in. of copper per core. 

Taking the cost 1 of these two cables at .£800 per mile and .£600 per mile 
respectively, the total cost is made up as follows 


Cost for 0-1875 sq. in. cables X 800 

” » 0-12 5 „ „ - 6 Mr X 600 


£4,620 

7,380 


33 per cent, for connections in power-house and sub-stations 2 
Total outlay for cables ...... 

oi £30 per kilowatt rated output of rotary converters installed. 

Take the cost of the rotary converters at £2*5 per rated kilowatt, and of the air 
blast tiansformers and ventilating motors at £1 per rated kilowatt, and sub-station 
switchboards and gear at £1 per rated kilowatt of sub-station. 

6 X 900 X 2 - 5 . . £13,500 for six rotary converters. 

21 x 300 X 1 0 . . £6,300 for twenty-one air-blast transformers and ventilating motors. 

6 X 900 x 1-0 . . £5,400 for switchboards and gear. 

A bile the abo\e costs are made up from round figures, they are fairly 
representative of the market prices of that date. If one were to lay out a plant of 
similai capacity using motor-generators, two-thirds as great total copper cross-section 
in the cables would be ample, less subdivision of the cables would be necessary, and 
tlnee independent cables from the power-house would give fully as great security as 
the foui cables employed in the rotary converter installation. Hence the individual 
cables would have but slightly less cross-sections of copper per core, and the specific 
cost would be but slightly increased. The cost for cables thus becomes 1*03 X 067 
X 16,000 = £11,000. 

Taking the cost of motor-generator sets as 75 per cent, higher than that of the 
rotary converters gives 

1‘75 X £13,500 = £23,600 for motor-generators. 

The transformer item falls out. 

The outlay for switchboards and gear may be taken two-thirds as great per 
kilowatt, since the number of panels, switches, bus-bars, etc., may be greatly reduced 
and simplified. 

Outlay for switchboards and gear = (£67 X £5,400 = £3,600. 

1 Rough published data for cost of cables may be found in Appendix VIII. of Mr. O’Gorman’s 
paper on the “Insulation of Cables” (“Proceedings of the Institution of Electrical Engineers” 
(1901), Vol. XXX., p. 680), in Mr. Earle’s paper on “The Supply of Electricity in Bulk” 
(“ Proceedings of the Institution of Electrical Engineers ” (1902), Vol. XXXI., p. 895), and in 
Mr. Stewart’s paper on “The Influence of Sub-station Equipment on Cost of Electricity Supply” 
(“Proceedings of the Institution of Electrical Engineers” (1902), Vol. XXXI., p. 1122). See also 
Chapter VIII., “ The High Tension Transmission Line.” 

2 This percentage is high in the case in question, because of the very short distance between 
sub-stations. 


£12,000 

4,000 

£16,000 


18; 





ELECTRIC RAILWAY ENGINEERING 

Table of Comparative Costs. 


High tension cables ..... 

Rotary 

Converters. 

£16,000 

Motor- 

Generators. 

£11,000 

Rotary converters ..... 

13,500 

— 

Motor-generators ....•• 

— 

23,600 

Step-down transformers and ventilating sets 

6,300 

— 

Sub-station switchboards and gear 

5,400 

3.600 


£41,200 

£38,200 


Whether the interest on this 7 per cent, less outlay for the motor-generator scheme 
would offset the 3 per cent, to 6 per cent, lower efficiency of operation would require 
a careful analysis of the operating costs. 

Moreover, it is highly probable that a still less proportional initial outlay for 
cables would be permissible with motor-generators, if the interest on the saving 
justified the decreased economy in operation. The cross-section of cables, so far as 
reliability in service is concerned, would be determined from the point of view of the 
permissible current density, or rather the permissible heating, and not from that of 
the permissible drop. 

It is by no means intended here to assert that in the Central London plant the 
use of motor-generators would have led to ultimate higher earning capacity ; but so 
much data has been given to the public on this particular plant as to permit of a fair 
comparison on the basis of published data. It serves to illustrate the basis on which 
a comparison should be made, and shows that with longer systems, requiring a greater 
proportional outlay for high tension cables, the balance tends towards showing an 
economic advantage to be gained by the use of motor-generators. 

To emphasise the importance of these considerations we propose to describe 
the case of an extensive tramway plant in a large city in South America in which the 
high tension cables installed were utterly inadequate for permitting of good automatic 
regulation of the voltage at the commutators of the rotary converters installed at the 
more distant sub-stations. The plant was provided with three sub-stations, A, B, and 
C, and the installation of rotary converters and cables, and the distances from the 
power-house to each of the sub-stations are set forth in Table LXVIII. 

Table LXYIII. 


Some Data of a Rotary Converter Installation. 


Designation of sub-station .... . 

A 

B 

C 

Number of 400-kilowatt rotary converters at each sub¬ 
station ........ 

8 

3 

3 

Number of rotary converters to be considered as reserve 

1 

1 

1 

Number of three-core high tension (0,650-volt) cables . 

2 

2 

2 

Cross-section per core, square millimetres 

30 

30 

30 

Length of each cable, metres .... 

3,400 

5,900 

8,300 

Length of each cable in miles .... 

2-11 

3-66 

5-15 

Resistance per core at 15 degrees Centigrade in ohms . 

1-92 

3-34 

4-69 


The regulation was calculated for sub-stations A and C ( i.e ., for the nearest 
sub-station and for the most distant), under the assumption in each case that both 
cables in the sub-station were in service, that two out of the three rotary converters 

188 















Full Load Voltages at Commutators of Rotary Converters. 


Sub-station A. 
(Nearest Sub-station.) 



f&rc&nC of FullLc&d Current) from Tfotary Converter 


Fig. 1(34. 



Sub-station C. 
(Farthest Sub-station.) 



Fig. 165. 



Fig. 167. 
















































































































































































































































































































































































































1206- 



THE SUB-STATIONS 

at each sub-station were running, and that the voltage at the generating station was 
maintained constant at 6,650 volts. 

In Figs. 164, 165, 166, and 167 the results have been plotted in curves. 

Fiom these curves we see the futility of employing reactance coils in this case 
to improve the regulation. 

The compounding of the rotary converters had been proportioned so that at 
rated load some 25 per cent, of the excitation was supplied by the series coils. The 
observed and calculated no- 
load and full-load phase 
characteristics of the rotary 
converters are given in the 
curves of Fig. 168. A 
higher percentage of series 
winding ought to have been 
employed at any rate in 
the rotaries in the most 
distant sub-station, and at 
that sub-station a lower 
ratio of transformation in 
the step-down transformers 
would have been prefer¬ 
able. The only radical 
remedy for such a case, 
however, consists either in 
substituting motor genera¬ 
tors or in greatly increasing 
the equipment of high 
tension cables. 

From the standpoint 
of capital outlay, designs 
for each of these two plans 
should have been prepared 
and compared. 

In an article contri¬ 
buted to The Electrical 
Review, 1 one of the present 
writers expressed himself 
on this question as 
follows:— 

“ A good deal has been 
written on subjects relating 
to the relative merits of 
rotary converters and motor- 
generators, low-speed and high-speed engines, and on parallel running. The three 
questions have a more decided bearing upon one another than appears to be realised, 
In fact, while the present article deals with no strictly new idea, it has been written as 


-o 

St 

V. 

c 


400 


200 - 




















































































































































































































































































7_ 

















3 

5. 





og 












A'* 

\\o- 

V 
















-s 

Su 

















V or 

\c 

\< 

> 

:? 


















































































§ 


§ 




Field Excitation — nmjoeres 


Fig. 


168. 400-k.w. Rotary Converter Characteristic 
Phase Curves. 

Full line curves = Calculated values. Dotted line curves = Observed values. 


1 “Choice of Type and Periodicity for Electric Traction Plant 
Beview, May 24th, 1901, p. 872. 


(H. M. Hobart): Electrical 


189 











































































ELECTRIC RAILWAY ENGINEERING 


the result of a conviction that the logical consequences of the experience of the last 
few years in these matters, have not yet been clearly appreciated. Though many 
writers bring out interesting and useful conclusions, all seem to have missed the 
main point. 

“ Polyphase transmission systems with rotary converter sub-stations have now 
been installed in large numbers and operated with very gratifying results. Whatever 
considerable difficulties have been met with in their operation, have been attributable 
to lack of sufficiently uniform angular velocity in the prime movers. The writer quite 
disagrees with a current opinion that “hunting” difficulties in rotary converters are 
ever due to causes other than those originating in this lack of perfectly uniform 
angular velocity in the prime movers; at any rate, any other causes are of the most 
subordinate importance. Given a uniform angular rotation of the generators, the way 
is perfectly clear for entirely satisfactory operation of the rotary converters without 
any damping or other equivalent auxiliary devices. A consideration of the matter of 
obtaining sufficiently close phase regulation in the generators, leads to the following 
observations :— 

“ Two entirely different classes of generating plant are at present being advocated 
by engineers, and there is not the slightest likelihood that within less than several 
years electrical manufacturers will be relieved from the necessity of supplying 
apparatus of two altogether different types. These two types are respectively those for 
high-speed and those for low-speed engines. Take as a representative instance the case 
of a central station to be equipped with several 1,000-h.p. units. In the one case these 
will be arranged to run at, say, 250 revolutions per minute, in the other at about 83 
revolutions per minute. In the former case the problem of operating rotary 
converters satisfactorily is greatly simplified. The customary lowest limit for the 
periodicity is 25 cycles per second. This—for the speed assumed—requires but 
12 poles. A further customary requirement is that the phase deviation from perfect 
uniformity shall never exceed 2'5 degrees, or 0‘7 per cent. Hence the displacement in 
space from the positions corresponding to absolutely uniform angular rotation must not 

exceed P ^ Pei cen ^‘ = 012 per cent, of the entire circumference. With an engine 


exerting a fairly uniform turning moment, and at the relatively high speed of 250 
revolutions per minute, this should not require an excessively large fly-wheel. The 
case would be very different for the low-speed generator. At 83 revolutions per minute 
36 poles would correspond to 25 cycles per second, and the angular deviation from 
uniformity would have to be less than 0‘04 per cent., which for the low speed of 
83 revolutions per minute would, for the best of such engines, require a tremendous 
fiy-wlieel. In practice a less close degree of regulation would probably be decided 
upon, and the rotary converters would be made to run satisfactorily by wrought-iron 
pole-faces, damping plates, or pole-face damping windings, or the generators might be 
equipped with similar devices. But these will not result in so satisfactory working 
as would be the case with a plant in which no such troublesome tendencies exist. 
Moreover, at least 1 per cent, or 2 per cent, of energy would doubtless be dissipated in 
such devices. For the low-speed plant the writer would be inclined to lower the 
periodicity to, say, one-third of the present customary minimum value — i.e., to 
8^ cycles per second, and to employ generators with but 12 poles. At this low 
periodicity, step-down transformers would be very expensive, and the writer would 
abandon rotary converters and equip the sub-stations with 6-pole high potential 
synchronous motors running at 165 revolutions per minute, direct connected to 

190 



THE SUB-STATIONS 

first-class 600-volt railway generators. The lower efficiency of such a set-as 
compared with step-down transformers and rotary converters—would be so nearly 
oflset by the decreased energy requiring to he expended in devices for overcoming 
hunting, as to bring the commercial efficiencies of the two plants within 2 per cent, or 
3 per cent, of one another. It must also be remembered that there are two distinct 
difficulties thus overcome, or at least greatly modified—first, the paralleling of the 
geneiators with one another; and, secondly, when that is successfully accomplished, 
it still remains an open question whether the combined parallel running is sufficiently 
free from angular deviations to deliver satisfactorily constant periodicity to the rotary 
conveiteis. I he writer agrees with the views of some other engineers that it is open 
to question whether the most liberal of fly-wheels will necessarily lead to satisfactory 
parallel i mining of the generators. Quite contrary, however, to the general opinion, 
the writer believes that the larger the momentum of the rotor of the rotary converter, 
the moie independent will it be of these disturbing tendencies. This latter opinion, 
however, does not affect the conclusions reached in the present article. 

Of the higliei cost of sub-station motor-generators as compared with step-down 
transformers and rotary converters, it may be said that the great simplification in switch- 
boaid appaiatus, the less need for close regulation in the high tension mains, the 
dispensing with all auxiliary devices required for voltage adjustment and the far less 
skilled attendance required, will largely or altogether offset the difference in cost. 
Moreover, the railway generator employed in the sub-station would be of the normal 
construction best suited for the requirements, and such a machine of the highest 
giade maj, owing to standardisation and keener competition, be obtained from the 
manufacturers at a cost much less in excess of that of a rotary converter than that 
represented by the intrinsic values of material and labour in the two machines. 

“ In concluding, the writer would sum up his opinion as follows :—For future 
tiaction piojects, the rotary converter should be superseded by the motor-generator, 
and the periodicity should be still further lowered for the case of very slow-speed 
steam engines ; but it may often still be advantageous to employ rotary converters, 
and at 25 cycles per second, for plants where the generators are direct connected to 
high-speed engines.” 

Subsequent events have slowly led up to a more general recognition of the 
correctness of this standpoint than was obtained at the time of writing. 1 

The Use of Accumulators in Sub-stations. 

For working in parallel with rotary converters, some different considerations arise 
from the case of working in parallel with generators. 

In Geimany, accumulators have been widely used in parallel with shunt 
geneiatois foi tramway plants, the characteristic of the generator falling preferably 
a great deal more than the battery characteristic. 

But the conditions corresponding to the operation of rotary converters in 
sub-stations, require for most satisfactory results, a reasonably good regulation. Thus 
one rarely permits in the high tension cables, more than 5 per cent, drop on the 
maximum probable load, and only by resorting to line and transformer reactance, 
potential regulators, Aliotli device, etc., can one vary materially the commutator 
voltage of the rotary converter. This is leading, in France and America, to the 

1 See contributions by Eborall in reply to this article : Electrical Review, June 7th, 1901, p. 963, 
and June 14th, 1901, p. 1009. 


ELECTRIC RAILWAY ENGINEERING 


gradual introduction as a standard system, of employing a compound-wound booster 
in series with the battery in parallel with the rotary converter. The battery 
and compound-wound booster in series have a resultant characteristic approximately 
a straight line, i.e., they have the same terminal voltage for all values of the 
charging and discharging current, and hence a comparatively trifling inherent drop 
in a shunt-wound rotary converter suffices to permit of adjustments such that the 
system regulates automatically, and the rotary converter delivers a constant load, 
which, according to the conditions from instant to instant in the circuit supplied, 
goes, either partly or wholly, directly to this circuit, or is devoted to charging the 
battery. The voltage is furthermore automatically maintained constant. 

In such a system the variations in load on the generating station would 
generally not much exceed 10 per cent.; hence one would at any time place in service 
only a sufficient number of generating sets to carry the average load at their most 
efficient point of working. Hence the generators would only require to have an 
overload capacity of about 25 per cent, for an hour or so, this being a very different 
state of affairs from supplying generating sets capable of carrying a load rapidly 
fluctuating in the ratio of one to two, or even more. In the same way the rotary 
converters are supplied on the basis of only a safe margin above constant average load. 

The high tension cables also only require to be large enough to have the 
prescribed drop at average instead of maximum load, and this introduces a very 
great saving. 

But it is fallacious to look for good results from this system under any other 
conditions than that a very liberal storage battery be installed, this not with the 
object of using it up to anywhere near its rated capacity, but, in the first place, in 
recognition of the fact that batteries still deteriorate, even with the best of handling, 
much more rapidly than at the guaranteed rate, in the second place, in order to 
secure thoroughly good voltage regulation, and, in the third place, to thus have for 
a short time, independently of the dynamo-electric machinery, a source of supply 
ample for handling the entire load. With anything less than this, one is obliged 
to provide spare sets to almost the same extent as for a system without accumulators. 

Take a case for illustration :— 

Suppose a sub-station is required for furnishing a 600-volt load having peaks 
touching a maximum of 2,500 amperes, but having an average load of only 1,000 
amperes. In this sub-station should be installed three 400-kilowatt rotary 
converters, one being spare, and an accumulator for 2,000 amperes for 1 hour. 
Only in the remotely possible case of an accident during time of heavy service 
shutting down the central station generators would there be any probability of 
drawing more than 75 per cent, rated discharge current from the battery, and even 
the entire load of 2,500 amperes is but 25 per cent, in excess of the rated discharge 
current. Normally the rotary converters would be adjusted to deliver 75 per cent, 
of their full load of 1,330 amperes, i.e., 1,000 amperes, constantly, the battery 
receiving part of this whenever the load falls below the average, and the battery 
supplying the peaks in parallel with the rotary converters. Hence the battery is 
never charged at a higher rate than 1,000 amperes (its normal charging rate is 
0’6 x 2,000 = 1,200 amperes), and at this rate of 1,000 amperes only when the 
external load is zero, which, of course, practically never occurs. The battery never 
discharges at a higher rate than 1,500 amperes, and this only for the most extreme 
peaks of the load. The booster would not be proportioned for 2,000 amperes—the 
battery’s rated discharge current—but for a maximum of 1,500 amperes : for in the 

192 


THE SUB-STATIONS 



Fig. 169. 


Booster Volt-Ampere Characteristic 
Curves. 


case of a disaster requiring the temporary shut-down of the central station, the 
booster would also shut down, and 
the battery would temporarily 
supply the line direct, sometimes 
at a somewhat reduced voltage 
according to the state of charge. 

Then, if the accumulator should 
be out of service, the three rotary 
converters would be required to 
handle the load, and could do it, 
as their normal rated capacity is 
8 x 666 = 2,000 amperes, and the 
maximum peaks do not exceed 2,500 
amperes. 

Another advantage of this 
larger accumulator, is that its in¬ 
ternal resistance is lower: hence for 
the loads at which it will be operated, 
its regulation and its efficiency are 
better; also somewhat less voltage 
is required of the booster (which 
makes up for the internal drop in 
the battery and in itself), and the 
boosters may be a trifle smaller. 

L nless, on comparative calculations, a plant, even with such a liberally pro¬ 
portioned accumulator, shows increased 
economy, considering both first cost, 
maintenance, and operating costs, no 
accumulator should be used, but the 
system should instead consist of gene¬ 
rating sets with ample spares, and 
high overload guarantees, and the 
equipment of high tension cables and 
of rotary converters (which latter 
should be compound-wound) should 
be proportionally liberal. 

But in the event of there being 
evident economy in spite of the liberal 
proportions of the battery, it will be 
of interest to map out the system a 
little more in detail:— 

A representative 2,000-ampere cell 
will have, when used as a buffer battery 
for 1,500 amperes, a voltage ranging 
from 2‘4 when fairly charged, down to 
1*8 at fairly low charge; the average 
may be taken at 2'05 volts. 

600 



Fig. 170. 


Battery Volt-Ampere Characteristic 
Curves. 


We should instal 


2-05 


= 294 cells. 


E.R.E. 


193 


O 




























































































































































ELECTRIC RAILWAY ENGINEERING 


Obviously when the pressure on no load has risen to 2*4 volts per cell, the battery 
pressure will be 700 volts. The excess of 100 volts must be offset by the reversed 

shunt-winding of the booster. As 
the charge falls, the shunt excita¬ 
tion must be weakened by the 
rheostat in the shunt field, down to 
2T volts per cell, when the shunt 
field is 0. Then the shunt field 
should be reversed again, and 
causes the booster to help out the 
battery for the range of from 2’1 
volts down to 1’8 volts per cell. 
When the voltage has reached the 
low value of 1'8 per cell, the accu¬ 
mulator voltage is but 1*8 X 294 
= 530 volts. Hence the shunt¬ 
winding must supply a range of 
700 — 530 = 170 volts ; and to 
be reasonably liberal, we must take 
it at 200 volts, i.e., 100 volts in 
each direction. 

The series winding of the 
booster must care for its own 
internal resistance and for the 
internal resistance of the accu¬ 
mulator. 

The apparent internal resistance of a representative 2,000-ampere-hour cell may 
be taken roughly as 

During charge.0’000152 ohm ; 

During discharge ..... 0’000112 ohm. 

Apparent resistance of 294 cells during charge = 00445 ohm. 

,, ,, ,, ,, discharge = 0’0330 ohm. 

Hence, at the normal condition of 2 - 07 volts, the voltage required to charge with 
1,000 amperes = 600 + 

1,000 X 0 0445 = 645 volts, 
and the terminal voltage 
when discharging with 1,500 
amperes = 600 + 1,500 X 
0*0330 = 550 volts. Hence 
the series winding must, on 
discharge with 1,500 amperes, 
add 50 volts, and when 
charging with 1,000 amperes 
must set up 45 volts in oppo¬ 
sition to the battery voltage. 

Hence the booster cha¬ 
racteristic curves must be 
those shown in Fig. 169. 

These booster characteristics combined with the battery volt-ampere 

194 



Fig. 172. Curves of Regulation of Rotary 
Converter, Battery and Booster. 



Fig. 171. Connection Diagram for Battery-Booster 
Set in Parallel with Two Shunt-wound Rotary 
Converters. 

B.C. I. and R.C. II. = Two rotary converters. 

A = Ammeter with zero in middle of scale. 

B = Booster. 

C = Battery. 

E = Rheostat in shunt field of booster. 

S = Shunt field of booster. 

T = Series field of booster. 

V = Diverter shunt to series field. 

Z = Reversing switch in booster’s shunt field. 






















































THE SUB.STATIONS 


chaiacteiistics, which are given in Fig. 170, give a practically constant voltage 
across battery-plus-booster, of 600 volts. 

The plan described makes use of the pure compound-wound booster. A number 




Rotaries deliver 

IOOO Amps. 

tOOO Amps 

Battery receives 

1.000 Amps 

800 

Amps 

External Load 

C Amps. 

200 

Amps 



1,000 Ampj. IOOO Amps. 

0 Amps. Battery deliverst.500 Amps. 

IOOO Amps. 2500 Amps. 


Fig. 1/3. Diagrams showing Subdivision of the Current between Rotaries and Battery. 


of iei\ excellent and advantageous modifications are often emplo} 7 ed. These are very 
thoroughly described in a series of articles in the Electrical World and Engineer (New 
York) for .June 8th, 15th, 22nd. 29th 


and July 6th and 18th, 1901. The 
articles are by Lamar Lyndon, and are 
entitled “ Storage Battery Auxiliaries.” 
Of these the first four articles are the 
more important as relating to possible 
use in traction work. 

But inasmuch as a rotary converter 
sub-station in its simplest form has 
already a good many necessary con¬ 
nections and switches, it would not 
appear desirable, if a booster battery 
set is added, to bring in any but the 
most simple form. The connections 
corresponding to this form are shown 
in Fig. 171. 1 

In Fig. 172 are given curves 
representing the voltage regulation of 
the rotary converter and of the battery, 
with booster for varying currents on 
each. 

The diagrams in Fig. 178 show 



Fig. 174. Curves showing Distribution of 
Load between Rotaries and Battery- 
Booster. 


Theie is amongst those described in Lyndon’s articles one especially interesting method 
covered by Hubbard’s United States Patent 651,664 (1890), so devised that, above a certain limit 
excesses of load are taken by the generator instead of by the battery. It would appear that this 
would probably act too sluggishly to protect a battery in rapidly changing traction loads. 

195 


O 2 


























































































ELECTRIC RAILWAY ENGINEERING 


2WC 


22.0C 


200 C 




I20C 


/ooc 


3 


eo o 


eoc 

400 

200 


the subdivision of the current between the two 400-kilowatt rotary converters and 
the 2,000-ampere-hour battery. 

The arrangement gives constant potential of 600 volts at the continuous current 

load for all values of the load. 

In Fig. 174 are given curves 
showing, for any value of the 
external load, the distribution of 
the load between the rotary con¬ 
verter and battery plus booster. 1 

The booster would be finally 
adjusted in operation so that the 
battery charge should remain about 
constant under the average con¬ 
ditions of the load, tending, taking 
the day through, neither to charge 
nor to discharge. 

To estimate the efficiency of 
such an arrangement, we must 
assume a load curve on the sub¬ 
station and work out the occur- 




•4- '8 \-Z 1-6 20 24 2 8 3Z 36 4 0 44- 48 5Z 

Minutes 

Fig. 175. Five Minutes Load Curve. lences. 

The load curve m Fig. 17o 

(assumed merely for illustrative purposes) for 5 minutes, averages 1,000 amperes. 

Table LXIX. gives the amperes during each 0*2 minute ii.e., each 12 seconds), in 

rotary converter and in battery. 

Average amperes = — = 590 flowing into, or out of, battery and booster. 

25 

Hence during these 5 minutes there have been sent into the battery 

O *2 

25^x^l2 = ^ampere hours ; i.e., in an hour 12 x 24*7 = 296 ampere hours. 

The same amount was taken out. This is equivalent to current flowing through 
the battery at the rate of about 600 amperes. The apparent internal resistance 
(averages of charge and discharge) equals 0’039 ohm. C 2 R loss = 14,000 watts. 
Increase this to 17,000 watts to include all further losses in battery at this current. 

The booster installed will be for a maximum capacity of 150 x 1,500 = 225,000 
watts or 225 kilowatts; but as this is the maximum, it will be designed for a maximum 
efficiency at about half-load, say 800 amperes and 130 volts. The efficiency of a set 
working under such widely varying conditions, will not be high ; it may be taken at 
80 per cent, for all loads to which it is subjected for any length of time, although in 
fact this will vary through the range from 60 per cent, to 90 per cent. 

As the load on the rotary converter is constant, its efficiency may be taken at 
94 per cent. 

Of the average current of 1,000 amperes going to the load, 300 amperes only 
reaches the load after passing into, and out of, the storage battery and booster. 


1 Sudden sharp peaks of load would tend to be taken by the rotary converter, because the 
inductance of the booster series field makes it act somewhat sluggishly. This is an advantage, 
as tending to protect the battery from momentary high loads. The tendency may be increased by 
introducing additional reactances in the booster circuit. 

196 



































THE SUB-STATIONS 

Assume that the booster is traversed by its average 600 amperes at a terminal voltage 
of 75. (This voltage varies widely according to the state of charge.) 

75 x 600 = 45,000 watts. 

At 80 per cent, efficiency this corresponds to 11,300 watts lost in booster. 

Booster loss = 11,300 
Battery loss = 17,000 


Total 28,300 


Table LXIX. 

Distribution of Current in Rotary Converter and Battery for a Period of Five Minutes. 


Time in Minutes. 

Amps, from Rotary 
Converter. 

Amps, into Battery. 

Amps, out of 
Battery. 

•0 

1,000 

600 

0 

•2 

1,000 

600 

0 

•4 

1,000 

600 

0 

•6 

1,000 

0 

1,500 

•8 

1,000 

0 

1,000 

1-0 

1,000 

0 

1,000 

1-2 

1,000 

0 

0 

1*4 

1,000 

0 

0 

1*6 

1,000 

0 

0 

1*8 

1,000 

400 

0 

2-0 

1,000 

0 

1,000 

2-2 

1,000 

0 

1,000 

2-4 

1,000 

0 

1,000 

2-6 

1,000 

0 

100 

2-8 

1,000 

600 

0 

3-0 

1,000 

600 

0 

3-2 

1,000 

600 

0 

3-4 

1,000 

600 

0 

3-6 

1,000 

600 

0 

3-8 

1,000 

600 

0 

4-0 

1,000 

600 

0 

4-2 

1,000 

600 

0 

4-4 

1,000 

200 

0 

4-6 

1,000 

200 

0 

4-8 

1,000 

0 

800 


• 

7,400 

7,400 


The total output from the two rotary converters, with its constant load of 1,000 
amperes, is 600 kilowatts. This, at 94 per cent, efficiency, corresponds to 638,000 watts 
input and to 600,000 — 28,300 = 571,700 watts delivered from the sub-station. 

197 




























ELECTRIC RAILWAY ENGINEERING 


Hence the net efficiency is 


571-7 X 100 
688-0 


89*4 per cent., say 89 per 


cent., as against the 94 per cent, that it would have been without the extra trans¬ 
formation. 

But, with the widely varying loads occurring in sub-stations with compound-wound 
rotary converters and no accumulators, the average efficiency could not be expected to 
exceed 92 per cent, when the converter’s full load efficiency is 95 per cent. 

These 294 cells would not be supplied for less than £8,000. 


Accumulator ........... 

Booster ............ 

Three 400-kilowatt rotaries at £900 each ..... 

Ten static transformers at £850 each ...... 

Switchboard, wiring, cables, and all other accessories in sub-station 
Sub-station building .......... 


£8,000 

1,000 

2,700 

3.500 
1,000 

1.500 


Complete cost per sub-station .... £17,700 


We must make a comparative estimate of the cost of all those amongst the above 
items which will be chosen differently according to whether an accumulator is or is not 
employed. This will require figures for the high tension transmission line and for the 
power-house and equipment. 

Assume five sub-stations, such as that described, each 6 kilometres distant radially 
from a central power-house. Each sub-station is loaded, as in the case described, with 
1,000 average amperes and 2,500 maximum amperes; in fact, we may assume for each 
a load curve equal to that already given. Take the transmission as three-phase with 
6,500 volts between cores, or 8,750 volts per phase. 

For the accumulator project:— 

Permit 3 per cent, loss in high tension cables corresponding to average load. 

Average load = 5,000 X 600 = 3,000 kilowatts. 

Efficiency of sub-station transformation (including step - down transformer) 
= 0-97 X 0-89 = 0-864. 

1*03 

Hence generating station output = 3,000 X Q-yoT = kilowatts, or 1,200 

kilowatts per phase. 

Amperes per phase = 320. 

Amperes per core of each of the five three-core cables = 64"0. 

Volts drop per core = 113" volts. 

Piesistance per core = P76 ohms, or 0'294 ohm per kilometre. 

This corresponds to a cross section of 58* sq. mm. per core and a weight of 517- 
kilogrammes of copper per kilometre per core. 

Now in all three cores of all five cables there are 3 X 5 X 6 = 90 kilometres, 
hence 46,500 kilogrammes of high tension copper. 

Estimating the cost of the complete cable, laid and jointed, at 7*50 shillings per 
kilogramme of contained copper, we arrive at a total cost for high tension cables, of 

£17,500. 

In the power-house should be installed four 1,300-kilowatt, 5,000-volt, 25-cycle, 
94-r.p.m., three-phase generating sets, one being a spare. They must be guaranteed 
on the basis of carrying satisfactorily about 25 per cent, overload for half an hour. 
Estimate these generators at £3,000 each and the engines at £6,000 each. 

198 






THE SUB-STATIONS 


Central Station :— 

Building.£20,000 

Boilers, pumps, piping, etc.12,500 

Exciter sets, switchboards, and cables .... 4,000 

Four 25-cycle, 5,000-volt, 94-r.p.m. three-pbasers . 12,000 

Four engines for direct connection to above . . . 24,000 


Total, Central Station . 72,500 

Fligh-tension cables.17,500 

Five sub-stations at £17,700 . 88,500 


Total.£178,500 


Without accumulators :— 

Should require four 500-kilowatt rotaries instead of three of 400-kilowatt output. 

Four 500-kilowatt rotaries ........ £4,000 

Fifteen static transformers.5,000 

Switchboard, wiring, cables, and all other accessories in sub-station 1,000 
Sub-station building .......... 1,800 

Complete cost for sub-station .... £11,300 


The high tension cables must in this case be large enough to carry the maximum 

2 500 

load of 2,500 amperes with only 4 per cent. drop. Hence f X X 46,500 = 87,000 

kilogrammes of copper. 

Estimating on the cost of the complete cable, laid and jointed, at 6 shillings per 
kilogramme of contained copper, we arrive at a total cost for high tension cable of 

T26,000. 

In power-house, two more generating sets would be ample, as the peaks would 
not come simultaneously on all five sub-stations. 

Hence — 


Central Station :— 

Building.£22,500 

Boilers, pumps, piping, etc. .... 18,800 

Exciter sets, switchboards, and cables . . 5,000 

8ix 25-cycle, 5,000-volt, 94-r.p.m. three-pbasers 18,000 
Six engines for direct connection to above . 36,000 


Total, Central Station . . 100,300 

High tension cables ...... 26,000 

Five sub-stations at £11,300 .... 56,500 


£182,800 


Suppose we take as the average efficiency of the sub-station from incoming high 
tension cables to outgoing low tension cables, including step-down transformers, 

With accumulators 0*89 x 0*97 = 0*864, 

Without „ 0-92 = 0-96 = 0*884 

(0*96 being taken for variably loaded transformers against 0‘97 for transformers with 
constant load). 


199 











ELECTRIC RAILWAY ENGINEERING 


We have taken the average loss in the high tension cables at 3 per cent, with 
accumulators, and the loss with maximum (peak) of load at 4 per cent, without 

accumulators, hence x 4 = 1*6 per cent, average loss. 

Z,dUU 


Hence the average efficiency from beginning of high tension transmission lines 
to beginning of low tension lines is 

With accumulators 0864 X 0’970 = 83*6 per cent., 

Without ,, 0\884 x 0’984 = 87'0 per cent. 


There remains to compare the annual running cost and interest and depreciation 
on the capital outlay. 


With Accumulators. 


The generating plant delivers, for 20 hours per day, a constant load of 
3,600 kilowatts at the point of maximum economy of the steam engines. Under 
such conditions we may take the cost for coal, oil, repairs, staff (but exclusive of 
amortisation), at 0’7d. per kilowatt hour. Hence the annual running cost is 


365 X 20 X 3,600 X 0‘7 
240 


£7,700. 


The plant cost ( i.e ., the portion compared) already worked out above is 

£178,500. 

This, at 5 per cent, interest, represents an annual expense of 0'05 X £178,500 = 

£8,900. 

Of this £178,500 value of plant, the accumulators represent 5 X £8,000 = 
£40,000, and the annual depreciation should be taken at 10 per cent., i.e., 

Annual depreciation of accumulators = £4,000. 

On the balance of £178,500 — 40,000 = £138,500, the depreciation should be 
estimated at 5 per cent., giving 

Annual depreciation on balance at 5 per cent. = £6,900. 

Total depreciation on the £178,500 = 4,000 + 6,900 = 

£10,900. 

Summary for plant with accumulators:— 

Running cost.4:7,700 

Interest on value of plant.8,900 

Plant depreciation ....... 10,900 


Total annual cost 


£27,500 


Without Accumulators. 

The efficiency from the beginning of the high tension transmission lines to the 
beginning of the low tension lines has been shown to be 87'0 per cent., as against 
83‘6 per cent, with accumulators. Hence the generating plant is only required to 
deliver an average load of 

or-- X 3,600 = 3,460 kilowatts. 

o ( *U 

But this, instead of being constant, may he taken as varying frequently from 
2,500 kilowatts to 4,300 kilowatts. Under these conditions the same coal economy 
cannot be obtained, and we will take the cost per kilowatt hour at 0 8 d., as against 0*7 d. 
for constant load. Hence the annual cost is 

365 X 20 X 3,460 X 0’8 _ _ Q ... 

24Q — -8,400. 


200 








THE SUB-STATIONS 


The plant cost (i.e., the portion compared) is 

£182,800, 

and at 5 per cent, interest represents an annual expense of 

0-05 X 182,800 = £9,100. 

The depreciation, on a 5 per cent, basis, is also £9,100. 


Summary for plant without accumulators :— 

Running cost ........ £8,400 

Interest on value of plant ..... 9,100 

Plant depreciation ....... 9,100 


Total annual cost .... £26,600 


Hence the comparative total costs are—- 

With accumulators ... ... ... £27,500, 

Without ., ... ... ... £26,600, 


the results only differing by about 3 per cent., which on the total annual cost, 
including low tension network, trains, wages, administration, etc., would make a 
negligible difference between the two systems. 

There is also but little to choose between the two systems from the standpoint 
of regulation, and nothing from that of reliability of service. 

From the standpoint of attendance, however, the plant employing accumulators 
would be at a disadvantage. It is doubtful if many engineers with long experience of 
accumulators, and with open minds, would advocate the plant employing accumulators, 
unless they could thereby obtain better financial results. 

Accumulator advocates will protest against the assumption of 10 per cent, annual 
depreciation as being too high. It is, on the contrary, much lower than is generally 
obtained in practice. 

Before leaving the subject of storage batteries as relating to electric railway 
engineering, it may be well to give the substance of a brief comparison once made by 
one of the present authors, of the prices of storage batteries in Germany, England, and 
America. While prices have tended downward since the time that this comparison 
was made, it is believed that the data will nevertheless he of value in investigating 
the relative merits of plants with and without batteries. 

Tables LXIXa. and LXIXb. were prepared from data and curves given in a paper 
by Highfield, read before the Institution of Electrical Engineers, on the 9th of May, 
1901 (Proceedings, Yol. XXX., page 1046). 

In general, the data given in these tables, which one ought to be able to take as 
a guide to storage battery prices in England, are, in agreement with other available 
data on storage battery costs in England, much lower than the costs in America and 
much higher than the costs in Germany. Thus, in a paper by Grindle, before the 
Institution of Electrical Engineers, February 26th, 1901, there occurs the following 
statement:—“ ... by employing a battery to deal with the demand over and above 
the mean load, it will require that there shall be installed, a battery capable of delivering, 
as a maximum, 300 kilowatts. The cost of a battery to comply with these conditions 
would approximate somewhere about £12 per kilowatt, including booster and switch¬ 
board arrangement, or an expenditure of £3,600.” 

A 500-volt battery was under consideration, and by “as a maximum” the author 
in this case doubtless means the one-hour rate. It is seen from the note at the foot 
of Table LXIXa. that it is based on 30 per cent, less capacity than corresponds to 
the maker’s guarantees, hence we must for comparison take from Highfield’s data the 

201 




ELECTRIC RAILWAY ENGINEERING 


cost of a 300 X 0’70 = 210 kilowatts battery. This is £18 per kilowatt, or 210 X 
18 = £3,800, i.e., 5'5 per cent, higher than the price quoted in Grindle’s paper. 

In the Street Railway Journal for July, 1901, is an article by Lamar Lyndon, 
entitled “ The Storage Battery in Railway Power Station Service.” In this paper a 
cost of £34,120 is given for a battery and booster equipment complete and installed. 
This is, on a three-hour discharge basis, a G,150 ampere-hour, 550 volt installation, 
i.e., 1,130 kilowatts for three-hour discharge. This would be equivalent to only 
1,130 X 0‘70 = 800 kilowatts, on Highfield’s rating, and his data shows a cost of 
about £32 per kilowatt. Hence, cost = 800 X 32 = £25,600, or 75 per cent, of the 
cost which Lyndon gives. 

In Germany, a Hagen battery, which the makers would guarantee for 2,000 
ampere hours on a one-hour discharge basis, would, complete with booster, installed 
for 550 volts, cost £8,000. This has a one-hour capacity of 1,100 kilowatts, but on 
Highfield’s basis of rating, only 770 kilowatts. 

Highfield’s data would show for this a cost of about £16'8 per kilowatt, or 
770 x 16’8 = £12,900, a price 61 per cent, higher than the price in Germany. 

Summary. 

Cost in Germany . . . . . =100 

„ England. J = 160 

,, America.= 210 

As to the weights of material in these three cases, and the relative guarantees 
received, we have not enough data to ascertain. The above figures, however, throw 
some light on the reasons why batteries are used most frequently in Germany, less 
frequently in England, and only very rarely in America. One can roughly take £30 
per kilowatt for large buffer batteries, as manufactured in England, and on the basis 
of the manufacturer’s ratings as here defined for a three-hours’ discharge. 

Table LXIXa. 

Cost of Battery-Booster Sets, including the Battery and Booster and Switch Gear complete 
and ready for work, but excluding the Battery House — One-hour Discharge Rate. 


500 Volts—One-hour Discharge Rate. 


Kilowatts 
Output at 
1-hour Dis¬ 
charge Rate. 

Volts. 

Amperes 
(1-hour Dis¬ 
charge Rate). 

Capital Cost in 
Pounds. 

Cost in Pounds 
per Kilowatt 
(Rated on the 
1-hour Dis¬ 
charge Basis). 

Permissible 
Amperes for 
Momentary 
Rate. 

Permissible 
Amperes for 
3-hours Dis¬ 
charge Rate. 

Kilowatts 
Output at 
3-hours Dis¬ 
charge Rate. 

3,750 

500 

7,500 

53,000 

14-1 

10.000 

3,750 

1,875 

750 

500 

1,500 

12,700 

16-9 

2,000 

750 

375 

875 

500 

750 

6,650 

17-7 

1.000 

375 

187-5 

225 

500 

450 

4,050 

18-0 

600 

225 

112-5 

150 

500 

300 

2,730 

18-2 

400 

150 

75-0 

75 

500 

150 

1,690 

22-5 

200 

75 

37-5 


At a 6-hours discharge rate, the amperes rate is 60 per cent, of that for a 8-hours discharge rate. 

The batteries consist of 240 to 250 cells, and the capacity is taken as 30 per cent, less than the 
full-rated capacity when the battery is new, so that at the end of a period, depending on the work 
and treatment of the battery, the actual capacity will be up to its rated value. 

Ihe gear is all designed to work at the one-hour l’ate—if designed for the three-hours rate, a 
reduction of about 10 per cent, would be made. 

This data is a re-arrangement of that in Highfield’s paper, “ Storage Batteries Controlled 
by Reversible Boosters,’ of May 9th, 1901. See Journal Institution of Electrical Engineers, 
Yol. XXX., p. 1046. 


202 






























THE SUB-STATIONS 

Table LXIXb. 

Cost of Battery-Booster Sets, includin'/ the Battery and Booster and Switch Gear 
complete and ready for ivork, hut excluding the cost of the Battery House — 
Three-hours Discharge Rate. 


500 Volts—Three-hours Discharge Bate. 


Kilowatts 
Output at 
3-hours Dis¬ 
charge Rate. 

Volts. 

Amperes 
(".-hours Dis- 
charge Kate). 

Capital Cost in 
Pounds. 

Cost in Pounds 
per Kilowatt 
(Rated on the 
3-hours Dis¬ 
charge Basis). 

Permissible 
Amperes for 
Momentary 
Rate. 

Permissible 
Amperes for 
1-liour Dis¬ 
charge Rate. 

Kilowatts 
Output at 
1-hour Dis¬ 
charge Rate. 

1,875 

500 

3,750 

53,000 

28-2 

10.000 

7,500 

3,750 

375 

500 

750 

12,700 

83-8 

2,000 

1.500 

750 

187-5 

500 

375 

6,650 

35-4 

1,000 

750 

375 

112-5 

500 

225 

4,050 

36-0 

600 

450 

225 

75-0 

500 

150 

2,730 

36-4 

400 

800 

150 

37-5 

500 

75 

1,690 

45-0 

200 

150 

75 


At a 6-hours discharge rate, the amperes rate is 60 per cent, of that for a 8-hours discharge rate. 

The batteries consist of 240 to 250 cells, and the capacity is taken as 30 per cent, less than the 
full-rated capacity when the battery is new, so that at the end of a period, depending on the work 
and treatment of the battery, the actual capacity will be up to its rated value. 

The gear is all designed to work at the one-hour rate—if designed for the three-hours rate, a ( 
reduction of about 10 per cent, would he made. 

This data is a re-arrangement of that in Highfield’s paper, “ Storage Batteries Controlled 
by Reversible Boosters,” of May 9th, 1901. See Journal Institution of Electrical Engineers, 
Vol. XXX., p. 1046. 


Design of Sub-stations. 

The design and lay-out of a sub-station is controlled by the area and shape of the 
site available. The whole of the plant should, if possible, be arranged on one floor, 
thereby minimising the attendance charges. With a large sub-station, the cost of 
land may make it necessary to build it double-decked. The path of the energy 
through the sub-station should be as short and direct as possible from the high 
tension lines to the outgoing continuous current feeders. In consistence therewith, 
the arrangement of plant across the station should be in the following order:— 

Entrance of high tension cables, high tension switchgear, transformers, rotary con¬ 
verting apparatus (motor-generators or rotaries), low tension continuous-current switch- 
gear. An arrangement of apparatus following on these lines is desirable in the interests 
of a maximum of simplicity. If the area is limited, or constrained to an irregular shape, 
departure from the simplest form may become unavoidable. We give subsequently 
detailed descriptions of several representative sub-stations from which the general 
trend of design can be followed. 

Arrangement of Switchgear .—The switchboard is located along one side or across 
one end of the station. For small sub-stations it is generally on the main floor with 
the converting apparatus, but with stations of large capacity, the switchgear is often 
arranged on a gallery. In the latter case the operator commands a view of the whole 
station, which may on occasions be of considerable advantage. It is standard practice 
to build the switchboard in three sections, consisting of a set of panels for the high 
tension switchgear, a set of machine panels, and a set of distributing feeder panels 
Where the high tension switchgear is of the remote control type, which is becoming 
common practice for high voltages, the oil switches are mounted in brick chambers 

203 

























ELECTRIC RAILWAY ENGINEERING 


some distance away from the switchboard. The first section of the board consists, in 
this case, of a low tension control board to deal with the current operating the oil-break 
high tension switches. Examples of these are given in the subsequent references 
to particular sub-stations. The control hoard is provided with pilot lamps, to indicate 
which high tension switches are closed. By such arrangements all the apparatus is 
manipulated by low tension switches, the high tension gear being completely isolated. 

The Starting of Rotary Converters. 

The starting and synchronising of rotary converters may be accomplished in any 
one of several ways. The simplest, at first sight, is to throw the alternating current 
terminals of the rotary converter directly on the alternating current low tension 
circuit, or else to have the low tension transformer terminals normally connected to 
the rotary converter, and to throw the high tension transformer terminals directly on 
the high tension mains. But this, although often practicable, has several dis¬ 
advantages. By this method the current rush at the moment of starting is generally 
greatly in excess of the full-load current input to the rotary converter, and as it 
lags in phase by a large angle, it causes a serious drop of line voltage, and 
affects the normal line conditions, to the serious detriment of other apparatus on 
the line. This large current gradually decreases as the rotary converter’s speed 
increases. The action of the rotary converter, in starting, is analogous to that of 
an induction motor. The rotating magnetic field set up by the currents entering 
the armature winding, induces, but very ineffectively, secondary currents in the 
pole-faces, and the mutual action between these secondary currents and the rotating 
field imparts torque to the armature, which revolves, with constantly accelerating 
speed, up to synchronism. Then the circuit of the rotary converter field spools is 
closed and adjusted to bring the current into phase. But when the armature is first 
starting, the field spools are interlinked with an alternating magnetic flux, generated 
by the current in the armature windings, and in normally proportioned field spools, 
with several hundreds or thousands of turns per spool, a dangerously high secondary 
voltage is generated in these spools. Hence they must be insulated better than field 
spools ordinarily are, not only between layers, hut between adjacent turns ; and wire 
with double or triple cotton covering should be used. However, the most frequently 
occurring breakdown due to this cause, is from winding to frame, and hence extra 
insulation should be used between these parts. 

The terminals of the different field spools should be connected up to a suitable 
switch, arranged so that the field winding may be conveniently broken up into several 
sections ; otherwise, if 1,000 volts or so are induced in each spool, the strain on the 
insulation between the ends of these spools in series and frame, is severe. 

At starting, this switch must always be open, and must not be closed until the 
armature has run up to synchronous speed, which is observed by the line current 
falling to a much smaller value. This special switch is then closed, and afterwards 
the main field switch, whereupon a still further decrease in the line current occurs, 
due to improved phase relations, and the process of synchronising is completed. 

By means of a compensator, this heavy current on the line at starting, may be 
avoided. The connections for a three-phase rotary with compensator, are as shown 
in the diagram of Fig. 176. 

At the instant of starting, the three collector rings are connected to the three 
lowest contacts, and thus receive but a small fraction of the line voltage. They, 
however, receive several times the line current; i.e., if the taps into the compensator 

204 


THE SUB-STATIONS 


winding are, say, one-fifth of the way from common connection to line, then the rotary 
converter has one-fifth the line voltage and five times the line current. As the converter 
runs up in speed, the terminals are moved along until, at synchronism, the collector rings 
are directly on the line. The corresponding arrangement with taps from the secondary 
windings of transformers is so obvious as not to require a specific description. 

Another difficulty encountered when the rotary converter is started from the 
alternating current end, is the indeterminate polarity at the commutator when the 
rotary is made to furnish its own excitation. Unless some independent source of 
continuous current is available at the rotary converter sub-station, the rotary is 
dependent for its excitation upon the polarity that its commutator happens to have at 
the instant of attaining synchronism. If there are two rotary converters at the sub¬ 
station, and the first comes up with the wrong polarity, then it may be allowed to run 
so, temporarily, till the second one is 
synchronised. The second one can be 
given either polarity desired, by using the 
first as an independent source of con¬ 
tinuous current. Then, from the second 
one, the polarity of the first may be 
reversed into the correct direction, and 
the second rotary converter shut down-. 

Obviously, however, this indeterminateness 
of the initial polarity constitutes a further 
inconvenience and objection to starting 
rotary converters by throwing them directly 
on to the alternating current line. But in 
the case of large capacity, slow-speed rotary 
converters, consequently machines with heavy armatures, it has been found practicable 
to control the polarity of the first machine when it is started up from the alternating 
current side. One must stand ready by the field switch as the machine approaches 
synchronism, when the pointer of the continuous-current volt meter will commence to 
vibrate rapidly about the zero mark, with short swings. These will finally be followed 
by a couple of fairly slow, indecisive long swings, in opposite directions from the zero 
mark. Near the maximum point of whichever of these swings is in the direction of 
the desired polarity, the field switch should be closed, and the machine will excite 
itself, provided the field terminals are correctly positive and negative. Otherwise 
—which might happen on the first run, or after alterations—the field terminals will 
require to be reversed. 

The required line current is greatly reduced by starting up the generator and 
rotary converter simultaneously. The latter is then, from the instant of starting, 
always in synchronism with its generator, and the conditions of running are arrived at 
with a minimum strain to the system. But the conditions of routine operation rarely 
render this plan practicable. 

The time ordinarily required to put converters into service when starting up with 
compensators on the alternate current side, is approximately as follows 1 

300 kilowatts . . . .45 seconds, 

1,000 . 75 

1,500 „.1*20 

1 These figures are taken from a paper by S. W. Ashe on “ The Relation of Railway Sub-station 
Design to its Operation,” Journal American Institution of Electrical Engineers, Yol. XXIV., p. 1101. 

205 
































ELECTRIC RAILWAY ENGINEERING 


It is possible to start more quickly, the following times having been recorded:— 
300 kilowatts . . . .16 seconds, 

1,000 „.40 

1,500 .,. 65 

This includes the time necessary to close the high tension switch on the trans¬ 
former, the time of starting by means of air-break lever switches, and the time 
required for closing the field switches, the direct current circuit breakers, and the 
line switch. 

Another method in use, is to have a small induction motor direct-coupled to the 
shaft of the rotary converter for the purpose of starting the latter with small line 
currents. 

The starting motor has fewer poles than the rotary converter and a higher 
synchronous speed, the motor thus being able to bring the rotary converter up to the 
synchronous speed of the converter. 

The main advantage of this method is the increased reliability, since each rotary 
has its own independent starting motor; the latter, however, is an extra expense. 
Another disadvantage is that, as the torque of the induction motor varies as the 
square of the applied voltage, a small drop in voltage will decrease the starting torque 
to such an extent that it may not be sufficient to start the set. 

Where there are several rotary converters in a sub-station, a much better way 
is that described in a British patent specification, in which the station is provided 
with a small auxiliary set consisting of an induction motor direct-coupled to a con¬ 
tinuous-current dynamo, the latter being only of sufficient capacity to run the rotary 
converters, one at a time, up to synchronous speed as continuous-current motors. 
When this speed is arrived at, and synchronism attained between the alternating 
current collector rings and the line, the switch between them is closed, and the rotary 
converter runs on from the alternating current supply. 

In many cases, a continuous-current system derives its supply partly from 
continuous-current generators and partly from rotary converters. In such cases, the 
rotary converter is simply started up as a motor from the continuous-current line, 
and then synchronised. 

This method is practicable if there is continuous current available at the sub¬ 
station switchboard. This will not be so if a sub-station is totally shut down, and in 
this case the previous method, emplo 3 ung an induction motor-generator auxiliary set 
is useful, the induction motor running on the alternating supply. 

Synchronising Rotary Converters. 

One has the choice of synchronising the rotary converter either by a switch 
between the collector rings and the low potential side of the step-down transformers, 
or of considering the step-down transformers and the rotary converter to constitute 
one system, transforming from low-voltage continuous current to high-voltage 
alternating current, and synchronising by a switch placed between the high tension 
terminals of the transformers and the high tension transmission line. This latter 
plan is, perhaps, generally the best, as for the former plan one requires a switch for 
rather heavy currents at a potential of often from 300 to 400 volts; and such a switch, 
to be safely opened, is of much more expensive construction than a high tension 
switch for the smaller current. Moreover, for six-phase rotaries, the low tension 
switch should preferably have six blades, as against three for the high tension switch. 

206 


THE SUB-STATIONS 



W 


03 

03 K 

£ B 
o r 


g o 
fe Ph 


o 

O 


H 

W 


oc 

i' 


£ 


GO 

£ 

<- 

g 

03 

M 

£ 


o 

£ 

C/2 


o 


o 

P3 

w 

cc 


o 

W '-■' 
fc C0' 

& o 

5 g 

, H 


^ o 
2 2 
o & 1 

<! Si 


to 


207. 





























































































































































































































































ELECTRIC RAILWAY ENGINEERING 


It is much simpler with six-phase rotary converters, to have an arrangement which 
obviates opening the connections between the low tension terminals of the trans¬ 
formers and the collector ring terminals, although in such cases some type of 
connectors should be provided which may be readily removed when the circuits are 
not alive, for purposes of testing. 

The arrangement shown in Fig. 177 represents a plan for synchronising and 
switching on the high tension circuits, and adapted to six-phase rotaries. 

Fig. 178 shows diagrammatically a plan for a three-phase system where the 
switching is done on the low tension circuits. 

Starting of Asynchronous Motor Generator Sets. 

Induction motor sets can be started, firstly, by switching the induction motor 
directly upon the high tension line and running up to speed by cutting out resistance 
in the motor circuit. 

This is a simple arrangement, and there is only required a variable resistance, 
which can be mounted with its switch on a pillar near each set, thus avoiding long 
cables for the heavy rotor currents from the set to the switchboard. If the motors 
have permanently short-circuited squirrel cage rotors, they can be started by means 
of a compensator in the stator circuit, as already described in connection with the 
starting of rotary converters. 

If any continuous-current is available at the sub-station, whether from a set already 
running, or from another sub-station, it is possible to start up a small auxiliary motor- 
generator set from the continuous-current side, running the generators as shunt motors. 

If this method is adopted, the induction motors may all have squirrel cage rotors, 
and no compensators in the stator circuits. However, in order to provide for the 
event of failure in the continuous-current supply, it is advisable to instal at least 
one set with a slip-ring induction motor, or with a compensator, so that it can be 
started up from the high tension side. 

Descriptions of Typical Sub-stations. 

We shall now gi\ T e technical data relating to the sub-stations on the following- 
railways which are representative of modern practice : — 

(1) Central London Railway; 

(2) Metropolitan Railway; 

(3) Metropolitan District Railway ; 

(4) North-Eastern Railway ; 

(5) New York Central and Hudson River Railroad ; 

(6) New York Subway of the Interborough Rapid Transit Co. 

The data for all of these lines are presented collectively in tabular form in 
Tables LXX. to LXXII., from which many interesting conclusions may be drawn. 

In addition to these data, there is gi\ r en a short description of one sub-station 
on each line which is typical of sub-station practice on that line. 

Table LXX. shows the total number of sub-stations on each line, the total 
number of converter sets, and their present and ultimate aggregate capacity. 

I able LXXI. contains a complete list of the sub-stations on all these lines, with 
technical data for each station. 

I he table shows the distance between sub-stations and their distance from 
the generating stations, also the number and capacity of the transformers and 
converters, with the aggregate capacity of each station. 

208 




Fig. 179. Central London Bailway. General Arrangement of Marble Arch Sub-station. 



















































































































































































































































































































































































THE SUB-STATIONS 

. In _ Tables LXXIL, for a number of typical sub-stations on each line, there is 

given the capacity and floor area, from which is worked out the kilowatt capacity 
per square foot of floor area. 

In the last column are entered remarks on the lay-out of the sub-station 
which would have a bearing on the values of the latter constant. 


Table LXX. 


Number of Sub-stations on various Electric Railways and their Capacity. 


Railway. 

Total 
Number 
of Sub¬ 
stations. 

I 

Num ber of Converters. 

Total Capacity. 

Installed. 

Ultimate. 

Installed. 

Ultimate. 

Central London Railway 

Metropolitan Railway. ... 

District Railway . . 

Great Northern, Piccadilly, and Brompton Railway 1 . 
Charing Cross, Euston, and Hampstead Railway 

Raker Street and Waterloo Railway 

North-Eastern Railway . . 

New York Central and Hudson River Railroad . 

Interborough Rapid Transit (The Subway, New York) j 

4 

8 

15 

)• 

5 

8 

8 

(12 ult.) 

8 

22 

35 

19 

14 

24 

8 

28 

49 

28 

20 

40 

98 

7.200 

18,800 

44,400 

17,600 

11,200 

27,000 

7,200 

24,000 

61,500 

26,000 

16.000 

45,000 

147,000 


1 The sub-stations on these railways are supplied from the District Railway Generating Station 
at Lot s Road. 


Table LXXI. 


List oj Sub-stations on various Electric Railways and Data regarding their Equipment. 


c? 

(3 

Sub-station. 

Distance in Miles from 
Generating Station. 

Distance in Miles to next 
further Sub-station 
along Route. 

Number 
of Stepdown 
Trans¬ 
formers. 

“J . 
a sh 

£ 1 
K ,0 

% CS 

0 

J Total Capacity 

1 of Transformers. 

Number of 
Converters. 

-:-1 

Capacity of each 
Converter. 

Total Capacity 
of Converters. 

In¬ 

stalled. 

Ulti¬ 

mate. 

In¬ 

stalled. 

Ulti¬ 

mate. 

In¬ 

stalled. 

Ulti¬ 

mate. 

In¬ 

stalled. 

Ulti¬ 

mate. 

O 

Shepherd’s Bush 

— 

1-61 

4 

4 

300 

1,200 

1,200 

1 

1 

900 

900 

900 

O 

Notting Hill Gate . 

1-61 

1-82 

7 

7 

300 

2,100 

2,100 

2 

2 

900 

1,S00 

1,800 


Marble Arch 

3’43 

0-44 

7 

7 

300 

2,100 

2,100 

2 

2 

900 

1,S00 

1,800 

•5 K 

Davies Street . 

3-87 

2-32 

7 

7 

300 

2,100 

2,100 

2 

2 

900 

1,800 

1,800 

O 

Post-office 

0-20 

— 

7 

7 

300 

2,100 

2,100 

2 

2 

900 

1,800 

1,800 


Ruislip .... 

775 

4’25 

6 

9 

300 

1,800 

2,700 

2 

3 

SOO 

1,600 

2,400 


Harrow .... 

3-50 

4-00 

6 

9 

300 

1,800 

2,700 

2 

3 

S00 

1,600 

2,400 

a 

Neasden .... 

— 

3 AO 

0 

9 

300 

1,800 

2,700 

3 

3 

SOO 

2,400 

2,400 

a 

Ph 

Finchley Road . 

3’25 

2-25 

9 

12 

300 

2,700 

3,600 

3 

4 

800 

2,400 

3,200 

C$ 

Gloucester Road 

8-50 

1-50 

9 

12 

300 

2,700 

3,000 

3 

4 

800 

2,400 

3,200 

O 

Bouverie Street 

7'00 

1-25 

9 

12 

300 

2,700 

3,GC0 

3 

4 

800 

2,400 

3,200 

+3 

Baker Street 

5-75 

1-00 

9 

12 

435 

3,915 

5,220 

3 

4 

1,200 

3,600 

4,800 


Euston Road „ . . 

6’75 

1’50 

0 

6 

300 

1,800 

1,800 

2 

2 

800 

1,600 

1,600 


Moorgate . . . . ! 

1 

8’25 

— 

G 

6 

300 

1,800 

1,800 

2 

2 

SOO 

1,600 

1,600 


E.R.E. 


209 


p 

















































































































ELECTRIC RAILWAY ENGINEERING 


Table LXXI. — continued . 





£ . 

0 - 

4-3 

X 

5 p 














c: 0 

p 0 

Number 












CC 4-; 

Ts © 

of Stepdown 

ci h 

Total Capacity 

Number of 

ce . 

Total Capacity 

>> 



— 4-5 

i v. p 

Trans- 

4- 5 

of Transformers. 

Converters. 


of Converters. 

ctf 

1 

a 

Sub-station. 


S to 

p P 

c* sc 

— UP 

formers. 

la 1 
I| 





oU 

1 ° 






O 2 

P - 
ci P 

Ip 

ci 

In- 

Ulti- 

O 

In- 

Ulti- 

In- 

Ulti- 

£ O 
cT 

0 

In- 

Ulti- 




so 

a u* 

stalled. 

mate. 

stalled. 

mate. 

stalled. 

mate. 

stalled. 

mate. 




p 

a 












Sudbury . 

■ 1 

9-59 

400 

6 

9 

300 

1,800 

2,700 

2 

3 

800 

1,600 

2,400 


Hounslow . 

• 

9-90 

4-50 

6- 

9 

300 

1,800 

2,700 

2 

3 

800 

1,600 

2,400 


Kew Gardens . 


6T0 

2-25 

6 

9 

435 

2,610 

3,915 

2 

3 

1,200 

2,400 

3,600 


Mill Hill Park . 


5-45 

2-25 

9 

12 

435 

3,915 

5,220 

3 

4 

1,200 

3,600 

4,800 


Ravenscourt Park 


3-27 

1-75 

6 

9 

550 

3,300 

4,950 

2 

3 

1,500 

3,000 

4,500 


Earl’s Court 


1-00 

1-00 

9 

12 

550 

4,950 

6,600 

3 

4 

1,500 

4,500 

6,000 

a 

Wimbledon Park 


5-83 

2-50 

6 

9 

435 

2,610 

3,915 

2 

3 

1,200 

2,400 

3,600 

o i 

P3 

4-3 

Putney Bridge . 


3'29 

1-75 

6 

9 

300 

1,800 

2,700 

2 

3 

800 

1,600 

2,400 

‘E 

South Kensington 


2-31 

1-50 

6 

9 

550 

3,300 

4,950 

2 

3 

1,500 

3,000 

4,500 

3 

Victoria 


3-72 

1-50 

6 

9 

435 

2,610 

3,915 

2 

3 

1,200 

2,400 

3,600 


Charing Cross . 


5-07 

1-25 

12 

12 

550 

6,600 

6,600 

4 

4 

1,500 

6,000 

6,000 


Mansion House 


6*37 

1-S7 

6 

9 

550 

3,300 

4,950 

2 

3 

1.500 

3,000 

4,500 


Whitechapel 


ST5 

1-75 

9 

12 

550 

4,950 

6,600 

3 

4 

1,500 

4,500 

6,000 


Campbell Road. 


10-35 

3-50 

6 

9 

435 

2,610 

3,915 

2 

3 

1,200 

2,400 

3,600 


East Ham . 


13-34 

— 

6 

9 

435 

2,610 

3,915 

2 

3 

1,200 

2,400 

3,600 

-r- 4^> - i 

Ct C M 

Golders Green . 


11-36 

2-25 

9 

12 

300 

2,700 

3,600 

3 

4 

800 

2,400 

3,200 

O ^ 03 

Belsize Park 


9T5 

2-25 

6 

9 

435 

2,610 

3,915 

2 

3 

1,200 

2,400 

3,600 

2.5 2^ 

o I^rQ p 

Baker Street 


7*37 

1-00 

6 

9 

300 

1,800 

2,700 

2 

3 

800 

1,600 

2,400 

£ o 

Hyde Park Corner 


3-34 

2-00 

(5 

9 

300 

1,800 

2,700 

2 

3 

SOO 

1,600 

2,400 

Xjlw . 

Euston Station . 


6-62 

1-00 

0 

9 

300 

1,SOO 

2,700 

2 

3 

800 

1,600 

2,400 

|-s.a 

co o a 

g “ c -o5 
s ■§ ® 

Kentish Town . 


8-30 

2-00 

6 

9 

300 

1,800 

2,700 

2 

3 

SOO 

1,600 

2,400 

Russell Square . 


5"62 

1-25 

(5 

9 

435 

2,610 

3,915 

2 

3 

1,200 

2,400 

3,600 

■*; CD 53 - ^ 

f c ^ s i 

Holloway . 


7-83 

2-50 

0 

9 

435 

2,610 

3,915 

2 

3 

1,200 

2,400 

3,600 

pOIZIQm 

xn 

London Road . 


6-42 

— 

6 

9 

1 300 

1,S00 

2,700 

2 

3 

800 

1,600 

2,400 


Pandon Dene . 


4-00 

4-00 

12 

12 

280 

3,360 

3,360 

4 

4 

800 

3,200 

3,200 

a> 

-p 

Cullereoats 


5"75 

5-75 

9 

12 

280 

2,520 

3,360 

3 

4 

800 

2,400 

3,200 

ci 

w 

Wallsend . 


0-25 

3-75 

9 

12 

280 

2,520 

3,360 

3 

4 

800 

2,400 

3,200 

+3 

o 

Benton 


2-50 

4-00 

6 

12 

280 

1,680 

3,260 

2 

4 

800 

1,600 

3,200 

525 

Kenton 


7 00 

4-25 

6 

12 

200 

1,680 

3,360 

2 

4 

800 

1,600 

3,200 

«♦-. r3 

o 5 

1. Grand Central Terminal 

0-36 

_ 

9 

15 

550 

4,950 

8,250 

3 

5 

1,500 

4,500 

7,500 

c <2 
c g 

+3 l-H 

O *-H 

2. Mott Haven. 

■ { 

5-47 

5 "49 


9 

15 

550 

4,950 

8,250 

3 

5 

1,500 

4,500 

7,500 

V i— 

X g 

3. Kingsbridge . 


9-44 

_ 

9 

15 

375 

3,375 

5,025 

3 

5 

1,000 

3,000 

5,000 

ci 7 ; 

.a u 

4. Yonkers 


15-64 

— 

9 

15 

375 

3,375 

5,625 

3 

5 

1,000 

3,000 

5,000 

lie 

5. Irvington 


22-11 

— 

9 

15 

375 

3,375 

5,625 

3 

5 

1,000 

3,000 

5,000 

T, o J| 

. C >H u 

<D 

6. Ossining 


30 31 

— 

9 

15 

375 

8,875 

5,625 

3 

5 

1,000 

3,000 

5,000 

7. Bronx Park . 


9-30 

— 

9 

15 

375 

3,375 

5,625 

3 

5 

1,000 

3,000 

5,000 

£ 

8. Scarsdale 


19-02 

— 

9 

15 

375 

3,375 

5,625 

3 

5 

1,000 

3,000 

5,000 


1 Hudson Division. 2 Harlem Division. 

210 










































































































THE SUB-STATIONS 

Table LXXI.— continued. 


1 

1 Railway. 

Sub-station. 

Distance in Miles from j 

Generating Station. 

Distance in M iles to next 

further Sub-station 

along Route. 

Number 
of Stepdown 
Trans¬ 
formers. 

Capacity of each 

Transformer. 

Total Capacity 
of Transformers. 

Number of 
Converters. 

Capacity of each 

Converter. 

Total Capacity 
of Converters. 

In¬ 

stalled. 

Ulti¬ 

mate. 

In¬ 

stalled. 

Ulti¬ 

mate. 

In¬ 

stalled. 

Ulti¬ 

mate. 

In¬ 

stalled. 

Ulti¬ 

mate. 


No. 11, Worth Street 

4-54 

1-70 

12 

24 

550 

7,600 

13,200 

4 

8 

1,500 

6.000 

12,000 

2 o 

No. 12, Union Square 

2-7S 

2-18 

— 

24 

550 

— 

13,200 

_ 

8 

1,500 


12,000 

p ^ 

No. 13, 8th Avenue . 

0-06 

2-08 

— 

30 

550 

— 

16,500 

— 

10 

1,501 

_ 

15,000 


No. 14, 90th Street . 

2-18 

2-27 

IS 

24 

550 

9,900 

13,200 

6 

8 

1,500 

9,000 

12,000 

^ $ 

No. 15, 143rd Street 

4-45 

2-55 

— 

24 

550 

— 

13,200 

— 

8 

1,500 

_ 

12,000 

J ^ 

No. 10, 132nd Street 

435 

2-08 

— 

24 

550 

— 

13,200 

— 

8 

1,500 

_ 

12,000 

-*-3 L-, 

— •—✓ 

No. 17, Hillside Avenue . 

7'05 

2-55 

— 

24 

550 

— 

13,200 

— 

S 

1,500 

— 

12,000 

—._ 

No. IS, Fox Street . 

7-46 

3-02 

— 

24 

550 

— 

13,200 

- 

8 

1,500 

— 

12,000 


Table LXXII. 

Floor Space of various Electric Sub-stations. 


Railway. 

Sub-station. 

Ultimate 

Plant 

Capacity. 

j Floor Area 
in Square 
Feet. 

Kilo¬ 
watts per 
Square 
Foot. 

Remarks. 

S ° cS 

Notting Hill Gate 

1,800 

830 

2-17 

I Sub-stations built in two circular 

H 

Marble Arch 

1,800 

830 

2-17 

j shafts sunk in the ground. 


Ruislip .... 

2,400 

2,790 

0-86 

Transformers on main floor. 

§ 1 

2^ 

Harrow 

2,400 

2,790 

0-86 

> > >i )> 

o — f 

k-H 

Finchley Road 

3,200 

3,660 

0-875 

> > > > yy 


Kew Gardens 

3,600 

2,140 

1-68 

Transformer or gallery. 


Mill Hill Park 

4,800 

2,760 

1-74 

>> yy yy 

c3 

£ 

Wimbledon Park . 

3,600 

2,140 

1-68 

yy yy yy 


Putney Bridge 

2,400 

1,880 

1-28 

yy yy yy 

-+=> 

o 

• rH 
rH 

Victoria 

3,600 

2,140 

1-68 

Transformers on main floor. 

in 

S 

Charing Cross 

6,000 

2,980 

2-00 

Transformers on gallery. 


Campbell Road 

3,600 

2,140 

1-68 

yy yy yy 


East Ham . 

3,600 

2,140 

1-68 

yy yy yy 

North- 

Eastern. 

Pandon Dene 

3,200 

3,840 

0-83 

Transformers on main floor. 


211 


P 2 






































































































ELECTRIC RAILWAY ENGINEERING 

Table LXXII.— continued. 




Ultimate 

Floor Area 

Kilo¬ 
watts per 
Square 
Foot. 

Railway. | 

Sub-station. 

Plant 

Capacity. 

in Square 
Feet. 

14 - r* 

° 5 

Grand Central Terminal 

7,500 

4,796 

1-56 






O 3 

Mott Haven. 

7,500 

3,845 

1-95 

133 



r— 

w g 

Kingsbridge . 

5,000 

3,845 

1-30 

c _ 






Yonkers 

5,000 

3,639 

1-37 

Jo H3 ^3 

5Q O 

Irvington 

5,000 

3,845 

1-30 






c| 

Ossining 

5,000 

3,845 

1-30 

OPH ^ 





K -1 > O 

Bronx Park . 

5.000 

3,845 

1-30 






Scarsdale 

5,000 

3,845 

1-30 

^ .12 £ 

No. 14, 96th Street 

12.000 

5,000 

2-4 

I Ilf 

No. 11, Worth Street . 

12,000 

6,000 

2-0 

Its s 

No. 16, 182nd Street 

12,000 

6,000 

2-0 


No. 12, Union Square . 

12,000 

4,400 

2-7 


Remarks. 


Each sub-station has battery 
equipment. 


Transformers on main floor. 


1. Sid>-stations on the Central London Railway. 

The sub-stations, as originally laid down, were built underground in circular 
shafts. The Bond Street Sub-station, which was put down since the opening of the 
line as an emergency station and chiefly for supplying lifts and lighting, is the 
only one which is on the ground level. The other stations are situated in the base 
of the lift shafts, below the level of the platforms, and are therefore at a depth 
of 120 ft. and more below the street surface. 

At Notting Hill Gate the whole of the equipment is contained in a single chamber 
30 ft. diameter and 21 ft. high, but at Marble Arch and at Post-office, the 
plant is divided between two chambers each 23 ft. diameter and 15 ft. high. 

Fig. 179 shows the general arrangement of the Marble Arch Sub-station, from 
which a good idea of the lay-out of the transformers, rotary converters, and switch¬ 
boards, may be obtained. 

The normal maximum output of each sub-station is 1,800 kilowatts, but this could 
be increased on occasion by 20 per cent, without any difficulty. 1 

The plant in each case consists of seven transformers, two rotary converters, 
and the necessary switchboards, blowers, etc. A novel kind of radial overhead 
crane, consisting of girders pivoted to the centre of the roof, and supported by 
wheels running on a circular rail at the circumference, provides for the ready 
handling of the machinery at Notting Hill Gate; part of this is visible in the 

1 A large part of this description of the Central London Railway sub-stations is taken by permis¬ 
sion from the Electrical Review for June 15th, 1900, pp. 1012—1018. It was prepared for 
the Electrical Review by Mr. A. H. Allen. 


































HOTTING HILL GATE SUBSTATION--- ' --- MARBLE ARCH SUBSTATION 



Fig. 181 . Central London Railway. Diagram of Connections of Two Sub-stations. 













































































































































































































































































































































































































THE SUB-STATIONS 

view of the main switchboard shown in Fig. 180. The two converters and the 
bank of transformers form three sides of a square, from the open side of which 



Fig. IsO. Central London Railway : Notting Hill Gate Sub-station Main Switchboard. 


a ladder leads to the switchboard gallery ; this extends half-way round the room 
at a height of 6 ft. 5 ins. from the floor level. 

In Fig. 181 is given a diagram showing the general arrangement of the 
connections of two of the sub¬ 
stations. From the connection 
boxes, one in each tunnel, two 
high tension feeder cables enter the 
room and pass through Parshall 
three-phase switches to the high 
tension ’bus bars which are 
mounted above the alternating 
current panels of the switch¬ 
board. An ammeter transformer 
is mounted on one of the bars to 
indicate the total current entering 
the sub-station; a view of this 
’bus-bar transformer is given in 
Fig. 182, which also shows the method of supporting the bars. Fig. 183 shows, at 
the left, the back of the high tension panels, with the Parshall switch-gear and 
volt meter transformers, as they appeared when erected at the maker’s works. 

213 



Fig. 182 . Central London Railway : Arrangement 
of High Tension ’Bus Bars and Ammeter 
Transformer. 


























ELECTRIC RAILWAY ENGINEERING 

Passing over a space in front of the ventilating trunk, the high tension 'bus bars 




High Tension Feeder Panel. Low Tension Feeder Panel. 

Fig. 183. Central London Railway : Back View of Sub-station Switchboard. 

High Tension and Low Tension Feeder Panels. 

bring the three-phase currents to three transformer panels shown at the left in 
Fig. 184. Each of these is fitted with double-pole switches for the primary and 




Transformer Panels. Converter Panel. 

Fig. 184. Central London Railway: Back View of Sub-station Switchboard. 

Transformer and Converter Panels. 

214 






































THE SUB-STATIONS 


secondary circuits of two transformers. Each of the latter has a rated output of 
300 kilowatts at a pressure of 330 volts on the secondary side when supplied at 
£ ,uuu volts ’ s0 that tlie normal secondary current is 910 amperes. The trans¬ 
formers are coupled up delta on both high and low tension sides. Fitr. 185 shows 



Fig. 184a. Central London Railway: Front View of High Tension Panels, 

showing Three-phase Switch. 


a view of the bank of transformers in place ; and Fig. 186 gives part sectional 
drawings showing their internal construction. It will be seen that the coils are 
supported in a vertical position, with a horizontal core in the form of a double 
magnetic circuit. 

The core is built up of steel laminae 0’014 in. thick, separately japanned, with 

215 
























ELECTRIC RAILWAY ENGINEERING 


ventilating ducts at frequent intervals. The steel is of special quality, having high 
permeability and low hysteresis losses, and alleged entire freedom, under the condi¬ 
tions of service, from deterioration due to ageing. The coils are wound on formers, 
in four primary and four secondary sections, arranged in series as shown in the plan. 
The transformers are cooled by an air blast, air being drawn through ducts between 
the coils and in the core; dampers are provided to regulate the draught by either 
path. There are two blowers driven by three-phase induction motors of 6 h.-p. each, 
with squirrel cage rotors ; these exhaust the air from a trunk beneath the trans¬ 
formers, to which the case of each is connected. The blowers may be used either 
singly or together, but one is generally sufficient. 



Fig. 185. Central London Railway: Notting Hill Gate Sub-station. 
Bank or 300 -k.w. Transformers. 


The six transformers are so connected with the switchboard that any or all of 
them may be used, and a spare transformer is held in reserve to replace any that 
may require inspection or repair. As will be seen from the curves of Fig. 187, the 
efficiency is high and well sustained, being 95 per cent, at quarter-load and over 
98 per cent, at full load. The analysis of the various losses is given with the 
efficienc} 7 curve. 

From the secondary switches of the transformers, three heavy ’bus bars carry 
the current to the converter panels, a back view of one of which is given at the 
extreme right of Fig. 184. Each of these is fitted with two Samuelson three-phase 
quick-break swatches, connected at the top with the ’bus bars, and at the bottom with 

216 


















THE SUB-STATIONS 


the leads to the alternating current side of the rotary converters 
have to break 2,000 amperes at 330 
volts on each blade, they are of 
very massive construction, and the 
phases are separated from one 
another by slabs of marble to pre¬ 
vent arcing. Fig. 188 shows one of 
these switches. 

Following the course of the 
current, we now come to the 
rotary converters. These machines 
are rated at 900 kilowatts output, 

1,800 amperes at 500 volts. Their 
overall dimensions are 11 ft. 8 ins. 
by 9 ft. 10 ins. by 9 ft. 9| ins. high. 

They are twelve-polar, and being 
fed with three-phase currents at 
25 periods per second, they run at 
250 revolutions per minute. The 
normal potential difference between 
the collector rings is 330 volts. 

In Fig. 189 we give a plan 
and sectional elevations showing 
their construction. The base 


As these switches 


\ -) 




t (_ 

— 


1 



O 

is 


casting 



Fig. 186. Central London Railway : Notting Hill 
Gate Sub-station. 300-k.w. Transformer, Eleva¬ 
tions and Plan. 


formed of a single iron 
supporting the bearings, magnet 
frame, and collector gear; the frame 
is of mild cast steel, to which the 
laminated steel magnet cores are 
bolted. The coils are wound on 
sheet iron spools with brass flanges; the shunt coil, of No. 11 B. and S., 912 turns per 

spool, is wound next to the yoke, 
and the series coil, of eight copper 
strips 2*5 in. by 0*075 in. in 
parallel, 2£ turns per spool, is close 
to the pole-pieces. The effect of 
compounding on a rotary converter 
is very interesting. Nominally the 
ratio of conversion from alternating 
to continuous current is invariable; 
but by causing the alternating 
current to lead or lag over the 
impressed E.M.F. it is possible to 
vary the effective pressure between 
the collector rings, so as to raise 
or lower the voltage on the com¬ 
mutator. For this purpose the 

Fig. 187. 300-k.w. Central London Railway Trans- armatures of the generators and 
former, Efficiency and Losses. rotaries, and the windings of the 



217 




































































































































































































ELECTRIC RAILWAY ENGINEERING 


static transformers, possess sufficient reactance, and the series winding on the 
rotary has the effect of over-exciting the fields, causing the current to lead in 
phase, so that as the load increases the continuous current voltage rises cor- 
respondingly. By suitably shunting the series winding, the compounding of the 
rotaries may be adjusted to give quite constant pressure under the widest variations 
of load. This subject has been dealt with at considerable length on pp. 175 to 186 of 
this chapter. 

The magnet cores are 12 ins. square overall, with a polar arc of 15f ins. 
on an internal diameter of 84'375 ins. ; the induction density in the cores 
is 95,000 lines per square inch, while in the yoke, which is 22 ins. wide, the 
density is 48,000. 




o 

o 

o 

“5 

|° 

o 

o' 

lol 

oi 

-2 

5° 




Fig. 188. Central London Bailway: Samuelson’s Triple Pole Quick Break Switch 

for Botary Converter. 


The magnet frame can be bodily slid along the bed-plate so as to completely 
expose the armature and field-magnet windings. 

The armature is built up of insulated sheet steel laminae 0'014 in. thick, secured 
by dovetailing to a heavy cast-iron spider. 

The overall diameter of the armature is 7 ft., and the inside diameter of the 
core 5 ft. 2 ins.; the gross length of the core is 12*5 ins. There are 288 slots, each 
1*25 ins. deep X 0 - 44 in. wide; the induction density in the teeth is 128,000 lines per 
square inch, and in the core itself 51,000 lines. 

The armature is of the drum type, multiple-wound with bar conductors; there 
are four of these in each slot, measuring 0‘4 X 0T25 in. each. 

The three collector rings are joined with the armature winding at eighteen equi¬ 
distant points; the rings are 24 ins. diameter by 3J ins. wide, mounted on a separate 
spider, and there are eight copper brushes to each ring. 

Ihe commutator is 54 ins. diameter by 17^ ins. long, and consists of 576 segments, 
can led on a cast-iron spider. There are twelve sets of carbon brushes, eight blocks, 
•G ins. vide by f in. thick, forming a set. These are carried by 7 a cast-iron ring supported 

218 




































































































































P I T 



77 8 



Fig. 189 . Central London Railway. 900 -K.W. Rotary Converter. 























































































































































































































































































THE SUB-STATIONS 

by brackets from the yoke, and can be adjusted simultaneously by a handwheel and 



Fig. 190. Central London Railway : 900-k.w. Rotary Converter 


S 

e 

* 

o 

£ 


o 

E 

v 


woim, though, in actual working, the brushes remain at the mechanically neutral point, 
whatever the load. 

The armature core weighs 
7,000 lbs., and the copper 721 lbs.; 
the total weight is 24,800 lbs. 

The magnet frame weighs com¬ 
plete 19,550 lbs., and the whole 
machine 48,850 lbs. Fig. 190 is 
a photograph of one of these 900 
kilowatts rotary converters. 

The curves of efficiency and 
losses of these machines are shown 
in Fig. 191. The overall efficiency, 
it will be seen, is 95 per cent, 
at full and overload, and 92J 
per cent, at half-load; it is not 
probable that the average load 
will fall below the latter value. 

The magnetisation curve (Fig. 

192), which is given in terms of 











—u. 

tj 

ad 



'j 



Full load 

ft In 



^flo 

ad 






















































to 










1 — 


"l 














Core 

loss 







Bear 

ng ai 

id all 

brus 

h frlql 

:iQQ-j 

v*in 

Jaae 


1 oa! 


re_ 

-irusl 

e$ 

1 R shunt field and rheostat _ 


-£ 

AR Series! 

- 1 

field amid 

—tt-'i 

r. 

4) 

> 


Ampere output 


Fig. 191. Central 
Efficiency and 
Converter. 

219 


London 

Losses 


Railway : Curves of 
of 900-k.w. Rotary 



















































ELECTRIC RAILWAY ENGINEERING 



Fig. 192 


Central London Railway : Magnetisation 
Curve or 900-k.w. Rotary Converter. 


both alternating and continuous-current voltage, shows the relation between these 
to be about 0'6 to 1 at practically all values of the magnetisation. The “ phase 

characteristic ” (Fig. 193) shows the 
great importance of accurately 
ascertaining the most suitable 
value of the field excitation, so as 
to obtain the best possible power 
factor. With the most favourable 
adjustment of the exciting current, 
i.e., with 6'4 amperes in the shunt 
winding, the “ apparent ” power 
factor on no load is only 0’7. When 
working on a load this value is 
exceeded, and it may be brought 
up nearly to unity by suitable 
excitation when fully loaded. 

The method of starting is as 
follows:—The first rotary must, of 
course, be run up on the alternating 
current side; three transformers 
are switched on, and the negative 
of the rotary. All other switches 
are left open, including special 
switches which divide the shunt 
winding into four short sections, for 
the purpose of avoiding the induction of an excessive E.M.F. in these coils. The high 
tension feeder switch and the three-phase rotary switch are then closed in succession, 
and the rotary starts up with 
about 2,000 amperes per col¬ 
lector ring. Full speed is 
reached in some 30 seconds. 

When synchronism is prac¬ 
tically attained, the field circuit 
is closed, care being taken to 
do this when the continuous 
current E.M.F. is building up 
in the right direction, as shown 
by the volt meter. If, however, 
the polarity is wrong, a fresh 
start may be made, or the 
second rotary run up ; if this 
also has the wrong polarity, 
one may be reversed from the 
other by means of the reversing 
field switch. Another method 
is to close all the necessary 
switches befoie the engine starts, and run up slowly. When one rotary is running, 
the others can be started as continuous-current motors from the line. For this pur¬ 
pose, the equaliser switch is thrown down, and the circuit breaker and field switch 

220 



Fig. 193. Central London Railway : Phase Charac¬ 
teristic of 900-k.w. Rotary Converter. 





































































THE SUB-STATIONS 

closed ; this excites the field of the incoming machine. The negative switch is then 
thiown downwards, and the starting rheostat closed step by step. The speed is then 
adjusted . to synchronism, and the three-phase rotary switch closed, after which 
the continuous-current switches are opened, leaving the converter running as a 

synchronous motor. The continuous-current side is then paralleled with the line in 
the usual way. 

Again following the current back to the switchboard, we arrive at the continuous 
cmient appaiatus. There are two panels, one for each rotary, on which are mounted 
the positive, equaliser, and negative switches. By throwing up the equaliser switch, 
the positive brush ring is coupled direct to the positive ’bus bar, the converter then 
limning as a shunt machine; when it is thrown down, the brush ring is connected 
with the equalisei bai for compound parallel running. When the negative switch is 
thrown upwards the machine is coupled with the negative ’bus bar through the 
circuit breaker, which is mounted above the corresponding three-phase switch ; the 
downward position couples the negative terminal with the negative ’bus bar through 
the starting rheostat. A Weston ammeter is fixed on each panel, as well as a double- 
pole reversing field switch and reversible field ammeter, and rheostat hand-wheel. 

A single, foui-point, staiting rheostat is mounted on one of the panels, coupled 
between the lower terminals of the negative main switches and the negative ’bus bar. 
An alternating current volt meter is provided which can be connected with the collector 
rings of either machine, as v 7 ell as a synchronising volt meter and lamps. 

The four feeder panels are fitted with circuit breakers and double-throw quick- 
break switches, as well as a Weston ammeter to each feeder. The third rail in each 
tunnel is cut by a section insulator near each sub-station, and the four ends are 
connected by feeders with the middle points of the feeder switches. These are arranged 
in pairs, two for the “up” tunnel and two for the “down.” The lower contacts°of 
each pair are coupled together by a short bar, so that when both switches are down, 
the third rail is electrically continuous and independent of the sub-station, and can be 
fed right through by the other sub-stations. In the upward position, the switches 
couple the positive ’bus with the third rail direct. 

The negative ’bus bar is permanently connected with the track rails, and the total 
energy supplied to each tunnel is separately recorded by two Thomson watt-hour 
meters. 

On the base of the feeder panels are mounted two three-phase switches controlling 
the blower motors, and a double-pole switch and starting rheostat for a series-wound 
Blackman fan motor, by means of which the sub-station is ventilated. 

The next panel carries the apparatus for controlling the lift cables; there are two 
of these running the whole length of the line, one in each tunnel. These are arranged 
on the same plan as the third rails in that by throwing down the switches the cables 
are coupled through and are independent of the station ; while by throwing them 
upwards they are connected with the positive ’bus bar. The current to the two “ up” 
cables is passed through an ammeter and a watt-hour meter, and through one circuit- 
breaker ; the same holds good for the “ down ” cables. The ammeter reads both sides 
of zero, so as to show the current restored to the line by the lift motors acting as 
regenerative brakes during the descent of the lifts. 

The lighting feeders are entirely separate from the power circuits ; a positive and 
a negative feeder for this purpose, run the whole length of each tunnel, and the distri¬ 
buting boards in each station are coupled with these on the three-wire system. The 
lighting feeders are connected with the -f- and — ’bus bars in each sub-station, and 

221 


ELECTRIC RAILWAY ENGINEERING 


with several storage batteries at different points on the line. The lighting panel, 
next to the lift panels, is fitted with a minimum current cut-out to prevent the 
batteries from feeding back into the machine; when this comes out, the lighting load 
is thrown entirely on the batteries, which also carry the load when the line is shut 
down. There is a positive main switch on this panel by means of which the positive 
lighting ’bus bar is coupled to the positive main ’bus bar, while the negative main 
switch is double-throw, to connect the negative lighting ’bus bar direct with the 


“The Engineer" 



A ir Shaft 

S'**- . 6 6 

: * 3'8i' 


. 7 &' - X-—7 6 .. 

800 HW. Rotary Converter 


"ra/n Ph 


4-'Steel 
Cable Over- 


Dram Pipe 


-U 7 s 


Fig. 194. Metropolitan Railway: Ruislip and Harrow Sub-stations. 


negative of either rotary, so that the lighting is unaffected by the circuit breaker. A 
main ammeter and a watt-hour meter are also provided for the lighting circuits. 

The remaining panel of the switchboard is fitted with various instruments by 
Weston and Elliott Brothers for testing the leakage from the third rail, the drop in the 
track rails, and the total return by earth to the sub-station. 

Fig. 180 shows the whole of the switchboard at Notting Hill Gate, except 
the high tension feeder panels. Figs. 188 and 181 show the backs of similar boards, 
and Fig. 184a shows the front of the high tension panels. 

The number of safeguards against breakdown, provided by the arrangement 
described, is worthy of note ; the sub-station can be supplied with power by either 






































































































































THE SUB-STATIONS 

01 both feeders from the power station; the transformers and converters are in 
c uplicate, and can be worked in various combinations ; the connections with the line 
and the lift cables are also arranged so as to give the maximum number of alterna¬ 
tives, and the storage batteries ensure that, whatever might happen to the line, the 
lighting would be unaffected. 

2. Sub-stations of the Metropolitan Railway. 

' Diawings of a typical sub-station are shown in Figs. 194 and 195, which relate to the 
Buislip and Harrow stations. The arrangement of the sub-station will be readily 



Swain Sc. 

Fig. 195. Metropolitan Railway : Ruislip and Harrow Sub-stations. 


understood. It will be seen that the transformers are in separate brick chambers, 
located underneath the switchboard gallery. An overhead traveller, carried on one 
side by steel pillars and on the other by stones projecting from the wall, serves 
to handle the transformers and rotary converters. Current is delivered from the 
mains at 11,000 volts, which is stepped down to 440 volts, at which it supplies the 
rotary converters, which deliver continuous current at 500 to 600 volts. 

The transformer efficiency is 97 per cent, at half-load, and 97‘4 per cent, at three- 
quarter load and full load. The temperature rise after 24 hours run on full load, is not 





























































































































































































































ELECTRIC RAILWAY ENGINEERING 

more than 45 degrees Cent., and at 25 per cent, overload not more than 60 degrees Cent. 
With a 50 per cent, overload for 1 hour, the rise is not to exceed 60 degrees Cent. 
The transformers are oil-insulated, self-cooling. The regulation is within 1*75 per cent, 
between no load and full load. Each sub-station is equipped with a high tension 
switchboard provided with oil break switches, guaranteed to break the full voltage at 
any load which may possibly come on the plant, these being for controlling the various 
high tension feeder circuits and the static transformers supplying the rotary con¬ 
verters. The instruments are all of low voltage, and are connected to the various 
cables through transformers. The low tension switchboards have marble panels 
carried in iron frames. The high tension switches are controlled by means of signal 
levers, actuated from the switchboard platform, and the high tension switchboard 



Fig. 196. District Railway : Plan of Charing Cross Sub-station. 


settings are built of special bricks, 8| ins. by 4^ ins. by 2f ins., laid with Yin- 
cement joints, the cement mortar being made in the proportion of one of cement to 
tw 7 o of sand. 

The rotary converters which are situated on the main floor with the transformers, 
have ten poles of laminated steel. Their efficiencies are— 

At half-loacl .... 91J per cent. 

At three-quarter load . . .94 ,, 

At full load . . . .95 ,, 

The machines are specified to be over-compounded for 10 per cent, increase in 
voltage between no load and full load. 

The temperature rise is specified not to exceed 40 degrees Cent, after 24 hours run 
on full load; with 25 per cent, overload, not greater than 50 degrees Cent., and with 
50 per cent, overload for 1 hour, not greater than 60 degrees Cent. 

224 






















































































































THE SUB-STATIONS 

The average voltage between segments is 11 volts, and carbon brushes are used. 
The guarantee as to sparking is that up to an overload of 50 per cent, no brush shift 

shall be required, and that with a temporary overload of 75 per cent, there shall be 
no serious sparking. 


3. Sub-stations of the District Railway. 

( sub-stations are arranged as shown in Figs. 196 and 197, which relate to the 

Charing Cross Station. The sub-stations are, with a few exceptions, built on land 
adjoining the railway, but at the Mansion House and at Victoria they are erected 
immediately above the railway tracks, and are supported on heavy girders. In these 
two stations, the general arrangement of Figs. 196 and 197 could not be adhered to, 
since, owing to “ ancient light ” claims of adjacent buildings, sufficient head-room 
could not be obtained. As may be seen from the figures, the main floor is occupied 
In the rotaiy converter sets and low tension switchboard. The transformers and high 
tension bus bars and switch-gear are erected on a gallery occupying the length of one 



side of the station. This gallery had to be dispensed with at Mansion House and at 
^ ictoria, and at these two stations the transformers are located on the floor with the 
rotaries. 

The Charing Cioss Station is the largest and most important of the sub-stations. 
Besides its own section of the District Railway, this sub-station will feed portions of 
the Bakei Stieet and Waterloo and of the Charing Cross and Hampstead lines. 

The high tension feeders, four in number, enter at one side and are carried to a 
“ high tension wall,” on which are mounted the high tension isolating switches. The 
eneigy passes thence to the step-down transformers on a gallery immediately in front. 

The switchboard is directly under the transformer gallery and on the main floor, 
w-ith the lotary converters. The ends of the floor space are occupied by an air 
compiessoi, a motoi generator, and blowers supplying the air blast for cooling the 
transformers. Below the ground floor is a basement for cables. 

iig. 198 shows a diagram of the connections at Charing Cross Sub-station, and 
Fig. 199 is a photo of a typical sub-station switchboard employed on this line. 

I he feeders on entering the sub-station are connected to isolating switches and 
e.r.e. 225 o 























































































































































































Ferda- ‘2 . . 

Spark gaps 



Fig. 198. District Railway : Diagram of Connections at Charing Cross 

Sub-station. 

226 





























































































































































































































































































































THE SUBSTATIONS 

spark-gap lightning protectors. Reverse current relays are provided at the sub-station 
nc o le Hg ension cables. Besides the usual instruments connected to the 
feeders, there is also a synchroscope, for indicating the phase before switching the 
ieedei through The main high tension bus bars are divided into four sections, with 
one feeder and one rotary converter connected to each. These bus-bar sections, by 
means of selector switches, may be operated independently or in multiple, as the case 
may require. Isolating switches are also fitted to each rotary converter circuit, thus 
piovidmg a flexible arrangement of connection. 

The secondary windings of the transformers are connected through three single 
pole knife switches to the collector rings on the rotary converter. The main high 
tension triple-pole oil switch for controlling each rotary, is hand-operated, but is also 



equipped with a polyphase overload time-limit relay. The continuous current side of 
the rotary is provided with two knife switches. A reverse-current circuit breaker is 
also inserted in the negative main. Each rotary converter is connected to an equaliser 
switch. The rotary converter is started by a small induction motor, and is operated 
from a corresponding panel on the alternating current switchboard. 

The lighting circuits are on the three-phase system. 

Switchboard —The total length of the switchboard is 69 ft. 4 ins. At the right- 
hand end of this board are six panels controlling the lighting circuits. These°are 
fitted with measuring instruments and double pole circuit breakers. In addition, the 
blowers for the air blast transformers are controlled from these panels. 

Adjacent to the sixth lighting panel are two instrument panels, carrying 
instiuments connected to the four high tension incoming feeders, and also two 
polyphase reverse current relays. 

2? 


O 2 
















ELECTRIC RAILWAY ENGINEERING 



Next fo the two instrument panels are four alternating current low tension panels 
for the rotaries. These panels carry the instruments used in connection with the low 
tension alternating current side, also the controlling switches, and the small motor 
starting switches. 

Following the alternating current panels, are four continuous-current panels for 
the rotaries. Each of these panels carries a circuit breaker with a reverse current 

relay attachment, and two 
single-pole knife switches. 
These panels also carry the 
rheostat dial switches for 
controlling the field windings 
of the rotary converters. 
After the continuous-current 
panels come the main load 
panels, carrying two large 
volt meters, one connected 
across the bus bars and the 
other to the machine volt 
meter. This panel also 
carries the main ammeter. 
Next to the load panel is 
the watt meter panel, carry¬ 
ing three large watt meters. 
Next come the lift panels, 
which control the supply of 
current to the lifts. Adjoin¬ 
ing the lift panels are placed 
twelve train section and 
track feeder panels. Each 
panel carries two 3,000- 
ampere circuit breakers, one 
4,000-ampere ammeter, and 
two 3,000-ampere single pole 
knife switches. The feeders 
are double pole, as the 
positive and negative rails 
are insulated throughout. 
The bus bars are of 

Fig. 200. District Railway: Type C. Oil Switch in C0 PP ei stiips. The low 

Sub-station. tension series transformers 

for operating the low tension 

alternating current ammeters consist only of a secondary winding and a magnetic 
circuit. The secondary windings are slipped over the switch studs, which form the 
primary of these transformers. 

The whole of the high tension cables, series transformers, etc., are mounted on a 
fireproof screen called the high tension wall. A series of small vertical brick cubicles 
or slots are formed in this wall, in which the cables are run. The high tension bus 
bars are arranged in similar cubicles. The spark gaps are arranged in a fireproof 
chamber. 


228 









THE SUB-STATIONS 

1 he switches installed for the high tension feeders and rotaries, are operated hy 
means of hand levers. These switches are automatically tripped by relays. The 
switch is main tamed in an open position hy gravity. Fig. 200 shows one of these 
switches, f hey are erected in a masonry structure, each of their three poles and the 
oil tank m which they are immersed, being in a separate fireproof compartment. 

4. Substations of the North-Eastern Railway. 

The electrified section of the North-Eastern Railway is served by five sub-stations 
having an aggregate capacity of 11,200 kilowatts. They are located respectively at 
Ran don Dene, Cullercoats, Wallsend, Benton, and Kenton. 

Of these the first-mentioned is the largest; it contains four converter units of 



800 kilowatts each. Next come Cullercoats and Wallsend, with three similar units • 
while Benton and Kenton each have two units. 

l he geneial arrangement of the sub-stations is shown in Figs. 201, 202 and 203. 
The generating station supplies the sub-stations with three-phase currents at a 
pressure of 5,500 volts, which is reduced by sets of three transformers in delta 
connection, and is converted hy the rotary converters into continuous current-at 
600 volts, at which voltage the current is supplied to the third rail. 

lhe high and low tension boards are located on opposite sides of the station, 

the piogiess of the energy from the high tension lines being thus from one side to the 
other. 

5,500-volt feeders (three-core, paper-insulated, lead-covered 

229 


The incoming 




















































































































































































ELECTRIC RAILWAY ENGINEERING 

cables), are fitted with spark gaps capable of relieving the cables of any abnormal rise 
of pressure. 

The main feeder switches between the feeders and the bus bars, are of the 



Fig. 202. North-Eastern Kailway: Longitudinal Section of Sub-station. 

Westinghouse oil-break type, as shown in Fig. 204. These are electrically operated 
from a low tension board, and are capable of breaking the maximum current of any of 



Fig. 203. 


North-Eastern Railway: Cross-Section of Sub-station. 


the sub-stations. The high tension gear is mounted on a fireproof wall, with parti¬ 
tions between each phase and circuit. In connection with the main feeder switches 
there are two reverse-current relays and solenoid switches which energise the tripping 

230 































































































































































































































































THE SUB-STATIONS 

coil and open the oil switch in case the current should reverse and the sub-station 
commence to supply power to the high tension feeders. A nine-panel low tension 
board is provided for the control of the high tension switch-gear. 

Electrically operated oil switches are also interposed between the bus bars and 
the high tension windings of the static transformers. These are fitted with time-limit 
overload cut-outs, to open in case of overload or breakdown. 

All high tension circuit breakers are provided with isolating switches, to ensure 



safety during inspection or cleaning. The current and potential transformers for 
instruments on the boards, are fixed between the high tension switches and the static 
transformers, or on the feeder side of the high tension feeder switches, as the case 
may be. One pole of each instrument transformer is earthed on the low tension side, 
to avoid any possibility of high tension at the operating board. 

The high tension switch-gear for the converter sets is controlled from panels on 
the large continuous-current board on the side of the station opposite to the high 
tension gear. 


231 














































ELECTRIC RAILWAY ENGINEERING 


Two panels are required for each converter set, one, as mentioned above, for the 
high tension side of the transformers, and the other for the direct current side of the 
rotaries. The group of three transformers and one rotary is treated as a unit, and all 
synchronising is done on the high tension side. A panel is also set aside for the 
transformers which supply the induction motors used for starting the rotaries. The 
load panels on this board carry instruments which measure the total power supplied 
to the traction feeders. They also carry suitable recording instruments. There 
are also six panels for the control of as many 600-volt feeders, each being fitted with a 
moving-coil ammeter, a circuit-breaker, and a knife switch. The negative poles of the 
machine and feeders are permanently connected to the negative bus bar. A small 
battery supplies current for operating the switches and for lighting the.pilot lamps. 
The main transformers are of standard Westinghouse oil-insulated and self-cooled 
pattern. They are each of 280 kilowatts rating at 5,500 to 360 volts and 40 cycles. 

The rotary converters, of 800 kilowatts rated capacity each, convert the 360-volt 
alternating current to 600-volt continuous current. Each rotary converter is a self- 
contained unit, the two bearings, the lower half of the frame, and the starting motor, 
being mounted on a common base plate. The temperature rise of the rotary converters, 
running continuously at rated load, does not exceed 35 degrees Cent., and at 50 per 
cent, overload, after three hours, 60 degrees Cent. Each rotary is started by a small 
Westinghouse, Type “ C.B." polyphase induction motor with rotor mounted on the 
armature shaft. This runs the armature up to speed before the main three-phase 
supply is cut in. Separate step-down transformers are provided for the supply of 
these motors. The lighting circuit is also supplied from these transformers. 

As already mentioned, the group comprising three three-phase transformers and 
one rotary converter is regarded as a unit. The following table shows the combined 
efficiencies of transformers and rotary converters, these being the average results of a 
large number of measurements :— 


Half-load . 
Three-quarter load 
F oil load . 
One-and-half load 


Efficiency. 

91 - 9 per cent. 


93-4 


>5 


939 


93-9 


5 ? 


A diagram of the electrical connections at Pandon Dene Sub-station is given in 
Fig. 205. 


5. Substations on the New York Central Railway. 

The data given in Tables LXX., LXXL, and LXXIL, for sub-stations on this line, 
relate to the New York City suburban section of the system. 

The power stations, two in number, are situated at Morris and Yonkers. These 
generate energy at 11,000 volts and 25 cycles, which is transmitted through mains, 
partly overhead and partly underground, to the sub-stations already listed in 
Tables LXX., LXXI., and LXX1I. Each sub-station may be fed from either power- 
station, and the lines are so disposed that no ordinary accident can cut off a 
sub-station from its power supply. 

At the sub-stations the high tension current is stepped down to continuous 
current at 666 volts for delivery to the third rail. The main equipment of each sub¬ 
station consists of three rotary converters and their accompanying transformers and 


THE SUB-STATIONS 


subsidiary apparatus, 
of five rotary converter 


I he arrangements provide for an additional future installation 
sets, as indicated in Tables LXX., LXXI., and LXXII. Each 



a 

o 

I—I 

H 

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H 

co 

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P 

m 

w 

a 

w 

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A 

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P 

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co 

A 

o 

H 

O 

W 

A 

A 

O 

O 

P 

O 

h-1 

rt 

H 

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w 

1-1 


p 

M 

uj 

P3 


(z; 

« 

W 

H 

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— 

— 

H 

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O 


10 

o 

cm 

6b 

s 


sub-station is provided with a battery equipment, and provision is made for any 
extensions that may be expected from increase in traffic. 









































































































































































































































































































































































































































ELECTRIC RAILWAY ENGINEERING 

The following general principles were adopted in the design of the sub¬ 
stations :— 1 

(1) The path of energy to be as direct and as short as possible from the high 
tension transmission line to the continuous current feeders ; 

(2) The wiring to be as little exposed as possible and yet to be readily 
accessible ; 

(3) All the machinery to be on the same floor as the operating boards ; 

(4) The principal apparatus to be under the direct control of the operator while 
standing at the operating boards ; 

(5) All apparatus and machinery to be so arranged that the effects of an accident 
shall be confined to the place where it occurs ; 

(6) The risk of accident to the operator to be as slight as possible ; and 

(7) Stations to be fireproof. 

In pursuance of the first idea, the apparatus is arranged in the following order, 
across the station :— 

Entrance of high tension lines, high tension switching apparatus, transformers, 
rotary converters, direct current switching apparatus. Along the station there is a 
succession of complete units, such as that described above, the controlling apparatus 
being located at the centre. The second requirement necessitated the use of wall 
chases for the high tension lines, and determined the use of transformers having both 
high tension and low tension terminals underneath the main floor. The third require¬ 
ment determined the omission of galleries except for lightning arresters. The fourth 
requirement introduced the use of electrically operated switches and circuit breakers 
for both the high tension alternating current and the low tension continuous-current. 
All of these switches and circuit breakers are operated from the control boards. The 
fifth requirement determined the ample spacing of the machinery and introduced a 
very complete system of barriers for the protection of line conductors, thus minimising 
danger to operators. 


Entrance oj High Tension Lines. 

The underground lines enter the basement through ducts, and are terminated at 
end bells, where they divide into three separate conductors running to three series 
transformers which supply current to the measuring instruments. The scheme 
adopted for the entrance of overhead lines was settled after a careful examination of 
all systems in use, and is believed to afford the best possible protection against rain 
and snow, not only to the incoming line, but also to the apparatus in the building. 


Liglitning A westers. 

The design of the lightning arresters w T as made with the view of separating the 
phases as much as possible and to make all parts accessible. The groups of arresters 
are mounted in such a way that a complete set may be taken out and replaced with 
the greatest facility, a feature which is believed to be original with this installation. 

All overhead lines are provided with knife switches to disconnect them from the 
sub-station apparatus. 

1 This account is extracted from the Street Bailway Journal report on the New York Central 
Railroad, Yol. XXVI., p. 920, November 18th, 1905. 

234 


THE SUB-STATIONS 


High Tension Wiring and Oil Sivitches. 

The high tension bus compartment is of concrete, and is provided with concrete 
barriers to separate the lines connected to the buses. The series transformers for the 
measuring instruments pertaining to lines and machines, are suspended from the 
ceiling in a row near the bus compartment, and are separated by barriers. In order 
to obtain this uniform arrangement, and yet leave the front terminals of the oil switch 
dead when not in use, the high tension lines between the series transformers and the 
power transformers are looped under the bus compartment, an arrangement which 
affords a very neat and practical way of combining two advantages which hitherto 
have not been jointly obtained. 

The wiring, where bare, is of copper tubing, which gives an excellent mechanical 
construction, a feature of special importance for the delta arrangement of the power 
transformers. The high tension bus bars are supported rigidly, but nevertheless in 
such a way as to take care of expansion and contraction. All openings in the bus 
compartment are protected by fireproof doors. 

The oil switches are electrically operated, and are designed to carry a substantial 
overload. They are provided with pilot lamps to indicate at the control board whether 
they are open or closed, and the lamp circuits are so arranged that there is no indi¬ 
cation unless the plungers complete their stroke without rebounding. The compart¬ 
ments are of brick, which matches the interior of the sub-stations, the barriers between 
phases being soapstone. 


Transformers and Rotary Converters. 

Two sub-stations are equipped with single-phase 550-kilowatt transformers to 
supply the 1,500-kilowatt converters, whereas the stations with 1,000-kilowatt con¬ 
verters have 375-kilowatt transformers. These have a normal ratio of 11,000 volts to 
460 volts, and are provided with extra taps for varying the voltage according to the 
drop in the transmission lines, or according to the distribution of load among the 
sub-stations. They are of the air-cooled type, with terminals underneath. The air is 
supplied by two induction-motor-driven blowers, one of which suffices to supply the 
station. 

The rotary converters are of the sextuple connection three-phase type, which 
combines the advantages of the ordinary three-phase and six-phase type. They 
convert the alternating current at 460 volts into continuous current at 666 volts. 


Continuous-Current Sicitcliboards. 

These will have motor-operated switches and circuit breakers, controlled from the 
boards at the centre of the station. The design of these switches and breakers 
is stated to ensure a certainty, rapidity, and safety of action hitherto unknown with 
this type of apparatus. A spare panel and auxiliary bus are provided, to which any 
feeder or machine may be connected pending repairs on its proper panel. All connec¬ 
tions are made with copper bars, thereby ensuring a neat and effective construction. 

The positive feeders after leaving the switchboards, are provided with end bells, 
which terminate the lead sheathing of the cables which run out to the third rail in 
underground ducts. 

The negative leads from the converters, run through the foundations and connect 

235 


ELECTRIC RAILWAY ENGINEERING 


to an ammeter shunt which carries the entire station output. The negative feeders 
are bare 2,000,000-circ.-mil cables, which run out directly to the tracks in pipes. 

There are two controlling boards situated at a part of the station which will be 
the centre when the station is extended to its final limits. There is a bench board 
which carries the principal instruments and control apparatus, whereas an upright 
board carries the auxiliary control apparatus for lighting, etc. All panels are of 
natural slate, with black finish, the instrument cases being black oxidised. 


Cranes. 

Each sub-station is provided with an electric travelling crane, which is also supplied 
with arrangements for hand operation. 


Storage Battery Equipment. 

The electric storage battery equipment is believed to be the largest railway battery 
installation in the world. It not only takes care of load fluctuations, but it is 
sufficiently large to operate the entire system under normal conditions for a period of 
1 hour in case of failure of generating apparatus. Five of the batteries have an output 
each of 2,250 amperes for 1 hour, and the others give 8,000 amperes, 8,750 amperes, 
and 4,020 amperes respectively. 

The batteries are located in buildings adjoining the sub-stations, and are operated 
in connection with boosters and switching apparatus in the sub-station. 

The discharge is governed by a carbon regulator, working in connection with 
exciters and boosters, the effect of which is to make the batteries discharge when there 
is heavy demand for current and to charge when the demand is light. 

The battery houses are of the most modern construction, and have acid-proof floors 
of vitrified brick. The heating and ventilating systems are of the most approved type, 
and are well protected against acid fumes. 


Starting Converters. 

Converters may be started either from the continuous-current or alternating 
current side. In the latter case a gradual application of voltage is ensured by taking 
current from several taps in the secondaries of the power transformers. Starting 
from the continuous-current bus, the machine is started as a continuous-current 
motor through a rheostat. When a speed above synchronism is reached, the 
continuous-current circuits, including the shunt field, are opened, and the machine 
runs by its momentum only. The alternating current is then put on by closing the 
oil switch, and the machine runs as a synchronous motor. It is then only necessary 
to close the shunt-field circuit to put the machine in synchronism. These operations 
are made to follow each other rapidly, and are effected by the use of a special 
combination switch. 


Lighting. 

Sub-station lighting is done with incandescent lamps operated by alternating 
current at 120 volts. The current is taken from the 460-volt power circuits and the 
\ oltage i educed by special transformers. The lights are distributed so as to illuminate 
all apparatus, and at the same time give a good general illumination. All wiring is in 

236 


THE SUB-STATIONS 


conduit, and circuits are con¬ 
trolled from standard panel 
boxes set in the walls. The 
lighting of battery rooms has 
been developed with a view to 
protection from acid fumes, all 
wiring in these rooms being 
lead-covered and all sockets of 
porcelain. Emergency lighting 
current may be taken from the 
control battery or charging set. 

Continuous-Current Feeder 
System. 

The continuous - current 
feeder system is designed to 
give a duplicate path for the 
current from the sub-station 
to the third rail. It is also 
designed so as to confine any 
trouble which may occur, to one 
track only, thereby making any 
interruption of traffic as slight 
as possible. Switches are pro¬ 
vided at the third rail to dis¬ 
connect all feeders at that point 
in case of a ground between 
the rail and the station. A 
train length section of third 
rail is separately fed from the 
sub-station, and is designed to 
prevent trains bridging between 
sections. All continuous-cur¬ 
rent cables are installed in tile 
conduits close to the tracks, 
except the auxiliary feeders 
which join the sub-station buses 
and supplement the conduc¬ 
tivity of the third rails. These 
are, in some localities, run 
overhead on the transmission 
poles. 

The four third-rails and 
auxiliary feeder are joined 
together through circuit 
breakers situated in small 
houses at intervals along the 
line, thereby increasing the 
effective conductivity. 





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Pig. 206. New York Subway : Converter Floor-Plan 
of Sub-station No. 14. 


237 





























































































































































































































































































































































































































ELECTRIC RAILWAY ENGINEERING 


6. Sub-stations of the Interborough Rapid Transit Co.; New York Subway. 

A list of sub-stations and corresponding data for each, is given in Tables LXX., 
LXXI., and LXXII. 

The converter unit employed to receive the alternating current and deliver direct 
current to the track, etc., has an output of 1,500 kilowatts, with ability to carry 50 per 
cent, overload for 3 hours. The average area of a city lot is 25 X 100 ft., and a 
sub-station site comprising two adjacent lots of this approximate size, permits the 
installation of a maximum of eight 1,500-kilowatt converters with necessary trans¬ 
formers, switchboard, and other auxiliary apparatus. 

In designing the sub-stations, a type of building with a central air well was 



Fig. 207. New York Subway : Cross-Section of Sub-station No. 14. 


selected. The typical organisation of apparatus is illustrated in the ground plan and 
vertical sections in Figs. 206, 207, and 208, and provides, as shown, for two lines of 
converters, the three transformers which supply each converter being located between 
it and the adjacent side wall. The switchboard is located at the rear of the station. 
The central shaft affords excellent light and ventilation for the operating room. The 
steel work of the sub-stations is designed with a view to the addition of two storage 
battery floors should it be decided at some future time that the addition of such an 
auxiliary is advisable. 

The energy is delivered to the line in the form of three-phase current at 11,000 
volts. 


238 







































































































































































































































































































































































THE SUB-STATIONS 



239 






































































































































































































































































































































ELECTRIC RAILWAY ENGINEERING 


The sub-station apparatus comprises transformers, converters, and certain minor 
auxiliaries. The transformers, which are arranged in groups of three, receive the 
three-phase alternating current at a potential approximating 10,500 volts, and deliver 
equivalent energy (less the loss of about 2 per cent, in the transformation), to the 
converters at a potential of about 390 volts. The converters receiving this energy from 
their respective groups of transformers, in turn deliver it (less a loss approximating 
4 per cent, at full load) in the form of direct current at a pressure of 625 volts, to 
the bus bars of the continuous-current switchboards, from which it is conveyed by 
insulated cables, to the contact rails. 

The illustration in Fig. 209 is from a photograph taken on one of the switchboard 
galleries. In the sub-stations, as in the power-house, the high pressure alternating 
current circuits are opened and closed by oil switches, which are electrically operated 



Fig. 209. New York Subway : Operating Gallery in Sub-station. 

by motors, these in turn being controlled by 110-volt continuous-current circuits. 
Diagrammatic bench boards are used, as at the power-house, but in the sub-stations 
they are, of course, relatively small and free from complication. The instrument 
board is supported by iron columns, and is carried at a sufficient height above the 
bench board to enable the operator, while facing the bench board and the instruments, 
to look out over the floor of the sub-station without turning his head. The switches 
of the continuous-current circuits are hand-operated, and are located upon boards at 
the right and left of the control board. 

A novel and important feature introduced in these sub-stations is the location in 
separate brick compartments of the automatic circuit breakers in the continuous-current- 
feeder circuits. These circuit-breaker compartments are shown in the photograph in 
Fig. 209, and are in a line facing the boards which carry the continuous-current-feeder 
switches, each circuit breaker being located in a compartment directly opposite the 
panel which carries the switch belonging to the corresponding circuit. This plan 

240 


















THE SUB-STATIONS 

will effectually prevent damage to other parts of the switchboard equipment when 
circuit breakers open automatically under conditions of short circuit. It also tends 
to eliminate risk to the operator, and, therefore, to increase his confidence and 
accuiacy m manipulating the hand-operated switches. 

Hie three conductor cables which convey three-phase currents from the power- 
iouse are carried through tile ducts from the manholes located in the street directly 
m iont of each sub-station to the back of the station where the end of the cable is 
connected directly beneath its oil switch. The three conductors, now well separated, 
extend vertically to the fixed terminals of the switch. In each sub-station but one 
set of high potential alternating current ’bus bars is installed, and between each 
incoming cable and these’bus bars is connected an oil switch. In like manner, 
between each converter unit and the ’bus bars an oil switch is connected into the high 
potential circuit. The ’bus bars are so arranged that they may be divided into any 
number of sections not exceeding the number of converter units by means of movable 
links, which, in their normal condition, constitute a part of the ’bus bars. 

Each of the oil switches between incoming circuits and ’bus bars is arranged for 
automatic operation, and is equipped with a reversed current relay, which°in the 
case of a shoit circuit in its alternating current feeder cable opens the switch and so 
disconnects the cable from the sub-station without interference with the operation of 
the other cables or the converting machinery. 


The Location of Sub-stations. 

Caitei has laid down in an interesting manner some important considerations 
which should contiol the location of sub-stations. To quote from his paper,^ 

In a system of any size there will usually be certain junctions from which 
se\eial lines radiate, and which accordingly form natural distributing points, where 
one would locate sub-stations if otherwise practicable. One must also locate a sub¬ 
station near each of the ends of a line, since, with the usual arrangement of low- 
tension feeders, the distance that one can feed to a dead end with a given drop in 
potential is only about one-third of the distance between adjacent sub-stations on the 
line. Sub-stations should, vdierever possible, be located at railway stations, for the 
convenience of attendants, inspectors, and visiting engineers, and to facilitate the 
delivery of supplies. 

I he above considerations having been taken account of, and local conditions 
fully allowed for, the sub-stations should be located with reference to the potential 
diop between sub-stations and trains. In the case of a completely insulated line 
equipment, such as that employed on the Metropolitan and Metropolitan District 
Railways, the waste of energy limits the mean voltage drop, whilst the necessity of 
efficient train lighting at all times limits the maximum. With a rail return, however, 
theie aie the additional restrictions imposed by the Board of Trade on the voltage drop 
in uninsulated conductors. 

“ The position of the trains with reference to the sub-stations should be mapped 
out, and the voltage drop in the conductor rails at any particular time determined. 
This should be done for a time of heavy load, and the worst condition to be anticipated 
in regular service should be judged, due allowance being made for probable future 
increase of traffic. 

1 '* Technical Considerations in Electric Railway Engineering,” paper read before the Institution 
of Electrical Engineers, January 25th, 1906. 

E.R.E. 


241 


R 


ELECTRIC RAILWAY ENGINEERING 


“ The location of the sub-stations will in the end be a matter of considerable 
adjustment and compromise, the object being to efficiently feed the system, employing 
as few sub-stations as practicable. On a system with many ramifications it is often 
impossible to prevent the sub-stations crowding one another somewhat in certain 
places, but, with care, the layout can usually be made so that there is not very much 
waste from this cause. 

“ In a continuous-current system, the all-day efficiency of distribution from gene¬ 
rating station ’bus bars to trains, is usually in the neighbourhood of 78 per cent. In 
a well-designed alternating-current system this efficiency would probably approximate 
to 87 per cent.” 

Mr. Carter is of opinion, and the authors most emphatically share the opinion, 
that this last-named advantage of systems employing single-phase equipments is 
more than thrown away when the rolling stock is considered. Indeed, while involving 
considerations which belong to a later chapter, we wish here to refer to another 
paragraph of Mr. Carter’s paper which reads as follows : — 

“ We can now see why, under suburban conditions, the single-phase system 
compares very unfavourably with the continuous-current system. What with the 
heavier train and the greater energy consumption per ton-mile, the energy consump¬ 
tion per train mile, for trains of given capacity, will generally be quite 45 per cent, 
greater under single-phase than under continuous-current operation. Allowing for 
the higher efficiency of distribution in the former of these systems, the power and 
energy generated must still be some 30 per cent, greater. This requires 30 per cent, 
greater capacity in the generating plant, the cost of which will almost wipe out the 
saving in the sub-stations, whilst the 30 per cent, greater annual generating costs will 
far exceed any possible saving in sub-station maintenance and supervision. In a 
compact system operating frequent trains—such as the usual urban system—the sub¬ 
station expenses are insignificant. The following proportions have been found to hold 
in reference to the Manhattan Elevated Railway:— 

Generating and sub-station expenses: — 


Maintenance, power-station 

. 90 

Operation, power-station 

. 85-0 

Maintenance, sub-stations 

. 0-5 

Operation, sub-stations . 

. 5-5 


100-0 


“ In estimating the capacity of the machinery in the several sub-stations, the 
number of trains fed by each sub-station at all times, must be estimated. A table 
should be drawn up showing the momentary maximum and average load on each sub¬ 
station, both at the time of heaviest traffic and at the time of light load. The output 
of the sub-station may be taken as 5 per cent, in excess of the input to the trains. 
The maximum momentary output may generally be taken as occurring when two 
trains are taking their maximum accelerating current, and all other trains that can 
possibly be supplied from the sub-station are taking their average current. This rule 
is, however, subject to modification according to the locality of the sub-station. 

“ When the above-mentioned table has been drawn up, the size and number of 
units in each sub-station can be determined. If possible, units of one size should be 
employed throughout the system, even if the capacity is sometimes greater than is 

242 




THE SUB-STATIONS 

^ T h 6 “ aximum momen tary output of the sub-station should be 

use The load TP « ^ maxmu,m momentary overload of the machines in 

se The load at times of heaviest traffic will indicate the number of units required 

and the output during the time of light traffic will be found useful in determini!,v the 
size of the units Having settled upon the number of machines required for service 
an extra one or two will usually be included in each sub-station to serve as a standby! 
m . . .“ e of rotary converter sub-stations, the total capacity of the installed 

machinery will usually be some 40 or 60 per cent, greater than that installed in the 
generating station for supplying power to the trains. The excess is chiefly required 
on account of the exceedingly bad load factor of a sub-station, which necessitates an 
installation far greater than the mean load would indicate. In this respect, the trans- 
oinier sub-stations of a purely alternating-current system show to great advantage. 

° lmeis can be designed to stand five or six times the rated load for short periods 
without injury or excessive voltage drop, and two or three times for an hour or two 
W1 out excessive heating. In such a system, therefore, the continuous capacity of 
su , s a ion p an ui usually be less than that of the generating station plant, since 
he former may be laid out to suit the mean all-day load, whilst the latter must suit 
the mean load at the time of the heaviest traffic”. 


243 


R 2 


Chapter VIII 

THE DISTRIBUTING SYSTEM 

B Y distributing system we mean that part of the electrical system separate from the 
generating or transmission systems and designed for controlling and regulating 
the voltage more or less independently of the voltage in the generating or transmission 
systems. Copper feeders may or may not be a necessary part of the distribution system, 
which may consist of either an insulated transmission rail with track return or of an 
overhead conductor with track return, or of either with an insulated return rail. 
Whenever the return is insulated, track feeders and the attendant disadvantages may 
be dispensed with, and this rule applies practically independently of the distance 
between feeding points. It will be seen that in practice the rail becomes an important 
part of practically any distribution system. This comes about from the fact that at 
high speeds a degree of rigidity is required in the collector system that is favourable 
to economical use of iron and steel as conductors. While the voltage in the 
transmission system may be allowed to vary to correspond with an economical use of 
materials, there are other conditions imposed by proper operation in the distribution 
circuit; for this reason the conductance of the distribution system must be relatively 
very high and cannot be widely varied to suit the economical working of material. 
Approximately constant voltage must be maintained in the operating circuit to 
ensure proper performance of train equipment. For this reason, together with the 
mechanical requirements, rails of very considerable cross-section are used, and in the 
best practice the drop in these rails rarely exceeds 2 or 3 per cent, of the pressure on 
the distributing circuit. The collecting device in the low tension system generally 
consists of shoes, which may be either under-running or over-running. With this 
class of collector, the surface is so considerable that practically any amount of current 
may be transmitted to a train without arcing or flashing, except when the most 
ordinary mechanical precautions are neglected. The chief objection which has been 
urged against a third rail system relates particularly to first cost, since even with the 
protected form, not more than 1,000 volts difference of potential between the conductor 
and rail is considered practical, even when the conductor rails are protected in the 
most efficient manner. In the case of the overhead system it is urged by its advocates 
that there is practically no limit to the safe working voltage. It remains to be 
proved by practical experience whether or not with the same conditions as to regu¬ 
lation, the overhead system is not more costly than the third rail system, since in 
general the third rail system has been designed with a small drop in pressure, 
whereas the overhead systems are generally designed with a considerable drop in 
pressure. The cost of maintenance of rail conductor systems has proved in practice 

244 


THE DISTRIBUTING SYSTEM 

negligible, whereas the maintenance of overhead systems is a considerable item in 
working cost. 

Preference is expressed by some railway engineers for some form of overhead 
construction, thus leaving the track clear of obstacles to the repair and upkeep of the 
permanent way, and also avoiding complications at junctions and termini. There are, 
howevei, a number of difficulties attendant upon the use of overhead construction, 
more especially with reference to high speed and to the small clearance under bridges 
and tunnels, which appear to have been overlooked. In order to allow of high speed, 
the conductor must be as free as possible from lateral movement, and at the same 
time must be flexibly suspended ; this is accomplished by suspending the conductor 
from a cable stretched longitudinally along and at a suitable height above the track. 
The bridges and tunnels oiler considerable difficulties to overhead construction owing 
to the limited head-room, and in extreme cases the conductor is transferred from above 
to the track level. The overhead conductor in these cases is sectioned and discon¬ 
nected from the source of supply and the current collected from a rail by a contact 
shoe. Provision for these requirements makes the high tension overhead system 
expensive, and may introduce great difficulties to safe or reliable working. One great 
advantage resulting from carrying the conductor overhead when placed at a uniform 
safe distance from the train, is that the conductor can with safety be charged to a 
higher voltage. 

The overhead system for railways is, by many, associated with alternating current 
motor equipments; there is, however, no essential connection between the two. 
Hitherto the vast bulk of electric traction throughout the world has been done by 
continuous current motors, and a pressure of from 500 to 1,000 volts between collector 
rail and earth has been found to satisfy the economical conditions and to be satisfactory 
piactice. 1,000 volts may be taken to be the safe limit of E.M.F. for rail systems as 
now constructed. Should the conditions demand it, there is no inherent difficulty in 
building motors for from 1,500 to 2,000 volts, which will stand the conditions to which 
railway motors are subject; tw T o such motors placed in series would admit of a line 
pressure of from 3,000 to 4,000 volts, at which pressure the current required to work 
the train is within the limits which can be transmitted by copper conductors of 
ordinary sizes and collected with trolley or bow. The limitations of the overhead 
system as to high speeds and heavy working, apply equally to both the alternating and 
continuous current systems. 

In distribution by alternating currents, regard must be had to their inductive 
action; we have to take account of the self-induction of the current on itself within the 
conductor, as a result of which the current tends to confine itself to the outer layers, 
and thereby increases the effective resistance of the conductor. This effect is negligible 
in copper conductors up to one half square inch cross section at a frequency of 25 cycles 
per second, which is the maximum frequency likely to be used in alternating current 
traction. Where, however, iron enters into a circuit, the effect is most pronounced, 
owing to the permeability of the material, and is of such magnitude that it cannot be 
neglected. There remains to be considered also the inductance of the circuit formed by 
the conductors, the effect of which, owing to the distance between the conductors, 
especially where one conductor is carried overhead, is considerable. There are other 
minor effects which are quite negligible, and need not be specified; the more important 
effects referred to above, will be dealt with quantitatively in subsequent sections of this 
chapter. 

Since the track rail is extensively employed for conducting the current back from 

245 


ELECTRIC RAILWAY ENGINEERING 


the motors to the point of supply, it is necessary to deal with the properties of a 
track as a conductor. We do not, however, deem it necessary to deal with the 

construction of the track generally, but only with such matters as are incidental 

to the use of the track as a conductor. 

THE THIRD-RAIL SYSTEM. 

The material of the third rail is chosen principally with reference to high 
conductivity, so far as cost permits, and with but little reference to wear, since it 

is only subject to the friction of a contact shoe pressed against it by gravity or 

occasionally by a comparatively light spring pressure. The strength of the section 
is of little importance, any section which is readily installed and insulated being 
suitable so far as relates to mechanical strength. The rail should be of sufficient 
cross-section to carry the current without undue voltage drop, and should present 
an ample contact surface for the collecting shoes. The chemical composition 



Fig. 210. Curve for Resistance and Composition of Steel. 


customarily employed, and the corresponding specific resistance, are set forth in 
Table LXXIII., on p. 248, the data in which relate to several third-rail systems. The 
composition employed in usual practice approximates to the following:— 

Carbon ...... 0*09 per cent., 

Manganese ..... 0*44 ,, 

Phosphorus. 0-088 ,, 

Sulphur. 0-080 „ 

The resistance of a rail of this composition is about 7"3 times that of copper. 
It is instructive to compare the constituents of conductor rails with those of track 
rails, given later on in this chapter. In the case of conductor rails, as mentioned 
above, the material is chosen especially with reference to a high conductivity rather 
tlian to mechanical properties, and on this latter account, the quantity of material 

246 











































THE DISTRIBUTING SYSTEM 

other than iron, present in track rails often reaches V5 per cent, (see pp. 267 to 271), 
while in conductor rails the quantity of other material present, as may be seen from 
Table LXXIIL, on p. 248, averages 0'5 per cent., and rarely exceeds 0’7 per cent. The 
resistance of such track rails is about eleven times that of copper, while that of 
conductor rails is only about seven times that of copper. Generally speaking, the 
lesistivity of a rail varies more or less in proportion to the amount of foreign material 
present, hut the cost of manufacturing a very high purity steel outbalances the gain in 
conductivity resulting therefrom, and hence a compromise is made between high 
conductivity and the cost of manufacture. 

While the resistance of pure iron is only about five times that of copper, the 
average for conductor rails is about seven times that of copper, which is not a great 



Fig. 211. Curves showing the Effect of Carbon and Manganese on the 

Conductivity of Steel. 


amount higher than the resistance of pure iron. Fig. 210 gives a curve showing 
the effect of foreign matter on the resistance of steel. This curve is deduced from a 
large number of test results of the General Electrical Co. of America, 1 and of 
Barrett, Brown, and Hadfield. It may be taken as giving fair values for any given 
percentage of total impurities, although, of course, the prevalence of each particular 
foreign element has its own characteristic effect on the resistance. To investigate 
the effects of such single elements, the tests carried out by the General Electrical 
Co. of America were made on a large number of samples of widely varying 
composition. By examining the samples with different proportions of, say, carbon, 
but with nearly constant proportions of other elements, the effect on the resistance, 
of varying the percentage of carbon could be studied, and in a similar way the effect 
of varying the percentage of any other element present. 

1 See paper by J. A. Capp, entitled “ The Electric Conductivity of Steel,’’ read before the 
American Institution of Mining Engineers, 1904. 

24; 



















































































ELECTRIC RAILWAY ENGINEERING 


Barrett, Brown, and Hadfield have ascertained that an increase in manganese 
from 0’5 per cent, upwards occasions a rapid increase in the resistance at first, and 
then more slowly until 7 per cent, of manganese is reached, after which the addition 
of more manganese has little or no effect. 

The effect of carbon is to increase the resistance directly in proportion to the 
percentage of carbon present. The curves shown in Fig. 211 indicate generally the 
quantitative effects of these two elements. 

The curve marked “ Manganese ” is for rails possessing a fairly low and constant 
quantity of carbon (from 0‘2 per cent, to 033 per cent.), the manganese being the 
principal variable between the limits set forth on the absciss® of the curve. The 
curve marked “ Carbon ” is for rails containing a fairly low and constant quantity 
of manganese (from 0’2 per cent, to 0'5 per cent.), the carbon being the principal 
variable element. 

Other elements present, i.e., sulphur, phosphorus, and silicon, are only permitted 
in such small quantities that the effect of their variation is fairly negligible. 

Table LXXIII. gives the chemical composition and conductivity of the conductor 
rails on several representative railways. 


Table LXXIII. 


Composition and Conductivity of Conductor Rails. 



Percentage Composition of Rail. 


Conductivity. 


Railway. 

Carbon. 

Man¬ 

ganese. 

Sulphur. 

Phos¬ 

phorus. 

Silicon. 

Total 
per cent, 
not Iron. 

Ratio of Specific 
Resistance of Rail 
to Specific Resist¬ 
ance of Pure 
Copper at 20° C. 

Microhms 
per Inch 
Cube. 

Resistance of 1 
Mile 1 Square 
Inch in Section 
at 20° C. 

Central London 

CO 

0 

•33 

•045 

•052 

Traces 

•457 

7-50 

4-94 

•313 

Baker Street and 
Waterloo . 

•05 

•19 

•05 

•05 

•03 

•370 

6-40 

4-25 

•269 

Manhattan 

•073 

•340 

•073 

069 

Nil 

•555 

7-750 

5T50 

•326 

Mew York Subway. 

•10 

•60 

05 

•10 

•05 

•90 

8-00 

5-30 

•336 

Boston Elevated . 

■037 

•341 

•073 

•069 

Nil 

•520 

— 

. 

_ 

Metropolitan and 
District 

•035 

•315 

•059 

•056 

Nil 

•465 




Great Northern and 
City . 







7-15 

4-42 

•280 

New York Central. 







7'50 

4-94 

•313 


Mounting of Conductor Rails. 

The method of mounting and insulating the conductor rail and the design of the 
insulator depend largely upon the shape of the rail section. 

Ibe insulating supports on which the rail rests are usually spaced from 
4 to 12 ft. apart. 

Some examples are given in Table LXXIIIa. for four London lines. 

248 


































THE DISTRIBUTING SYSTEM 

Table LNXIIIa. 

Showing Spacing of Insulating Supports. 


Railway. 

Distance in Feet between 
Insulators. 

Number of Insulators per 
Mile of Conductor Rail. 

Metropolitan and District 

10-5 

508 

Central London . 

7-5 

705 

City and South London 

6-5 

812 

Waterloo and City 

7-5 

705 


The weights per yard of the various conductor rails together with a number of 
other particulars of the track may be found by reference to Tables LXXIY., LXXYII 
and LXXVIII. 1 


Table LXXIY. 


Particulars of Conductor Bails for various Railways. 


tp 

+3 _. 


Particulars of Conductor Rail. 


Designa 

Number 

Railway. 

Length in 
Feet. 

Weight in 
Pounds per 
Yard. 

Cross- 

section. 

See Fig. 222, 
on p. 258. 

Area, Cross- 
section 
in Square 
Inches. 

1 

Paris Metropolitan . 


93 


9Y5 

7- 38 

8- 37 

8-37 

7-87 

6-Q 

2 

New York Subway . 

40 and 60 

75 

A 

3 

4 

Boston Elevated .... 

Central London 

60 

30 and 42 
42 

85 

85 

A 

D 

5 

Great Northern and City Railway 

80 

D 

6 

Lancashire and Yorkshire Railway . 

60 

70 

A 

7 

8 

Berlin Electric Overhead and Underground 
Berlin-Zossen . 

39 ft. 44 ins. 

56-5 

A 

5-6 

9 

Valtellina . 





10 

City and South London . 

30 

40 

D 

4-n 

11 

Baker Street and Waterloo Railway 


85 

E 

8-37 

12 

Petaluma and Santa Rosa Railway, California 

_ 



13 

Milan-Varese-Porto Ceresio Railway, Italy 

39 ft. 4 ins. 

90-7 

A 

9-2 

14 

St. Georges de Commires la Mure, France 

_ 



15 

Liverpool Overhead . 

32 



4-0 

16 

Mersey Railway, Liverpool 

60 

100 

T section 

9-8 

17 

Manx Electric Railway, Louglas-Ramsey 

_ 




18 

Seattle-Tacoma 

30 

100 

A 

9-8 

19 

Jackson and Battle Creek Railway . 

30 

70 

A 

6-9 

20 

Manhattan Elevated 

60 

100 

A 

9 - 8 

21 

Metropolitan District Railway . 


100 

A 

9-8 

22 

London, Brighton, and South Coast Railway . 

_ 



23 

New York Central 


70 

B 

6-Q 

24 

Paris-Versailles 

59 

94 

B 

9'26 

25 

North-Eastern ..... 

‘ 


80 

B 

7-8 


The material of the insulators themselves, should combine mechanical strength 
and durability with good electrical insulating properties. As these two properties do 
not usually exist together, it is somewhat difficult to obtain a satisfactory material. 

The material in most common use is of the earthenware variety. Thus the 


1 For Table LXXVII. and LXXVIII., see p. 272. 

249 




















































ELECTRIC RAILWAY ENGINEERING 

Baker Street and Waterloo Railway employs vitrified earthenware; the Central 
London Railway and the Metropolitan and District Railways of London are 







Fig. 212. Methods of Mounting and Insulating Conductor Rails. 

employing highly vitrified porcelain. These insulators were manufactured by 

Messrs. Doulton. 

The New York Central Railway, 
which has adopted the under-contact 
type of conductor rail, described here¬ 
after, is still experimenting with the 
following substances with a view to 
finding the most suitable: vitrified clay, 
rubber and indurated fibre and recon¬ 
structed granite. Reconstructed granite 
is employed on the Manhattan Elevated 
Railway. 

A number of methods of mounting 
insulated rails of Yignoles, bull-head, 
channel, and solid section are shown 
in Fig. 212. The diagram shows the 
customary methods of mounting rails of 
each of these sections, although special 
means are employed in exceptional 
cases. A reference to Figs. 220 and 221, 



Fig. 213. Conductor Rail Insulator. London 


Underground Electric Railways Co. 

which show sections through various tracks, will be instructive in this connection. 

250 























































































THE DISTRIBUTING SYSTEM 

The methods set forth in Fig. 212 are lettered A, B, C, etc., and a reference to 
column 3 of Table LXXY. will show the method in use on many of the roads enumerated 
m that table. The commonest method (Fig. 212a) of mounting a flat-bottomed rail, 
is on a cylindrical drum insulator, with some kind of overhanging tip clamping the 
bottom flange of the rail. A view of the London Underground Electric Railways Co.’s 
insulator is shown in Fig. 213. This consists of a black or cream enamelled 

vitrified stoneware of Messrs. Boulton’s manufacture, with base and cap of malleable 
cast iron. 

The method shown in Fig. 212c is employed on the Paris-Orleans Railway, where 
a bull-headed rail is mounted and insulated on timber. 

Fig. 21 2d shows mounting for a rail of channel section, as on the Central London 
Railway and on the City and South London Railway. The channel rail covers in the 
insulators, thus protecting them, and giving a highly satisfactory arrangement. It is 
surprising that the channel rail 
has not been used to a greater 
extent, as it has proved more 
satisfactory than an} r others, in 
cases where it is emploj^ed. 

For mounting a solid type 
rail Fig. 212e shows a simple 
solution, where the rail is laid on 
earthenware insulators bolted on to 
the sleepers with wrought iron clips. 

This type of rail and mounting 
is used on the Baker Street and 
Waterloo Railway, the solid square 
section being employed to save 
space, an important matter in a 
tube railway, and at the same time 
to get a large cross-section of rail. 

Wood is inferior to other insulating materials on the grounds of destructibility by 
weather and low durability. 

In designing the insulators, they should be relieved of undue stress, and should 
permit of sufficient freedom to the rail with regard to expansion, irregularities of track 
construction, and so forth. 

Fig. 214 shows another Doulton pedestal type insulator, somewhat similar to 
those employed on the District Railway. 

In Fig. 215 are shown two types of insulator by the Reconstructed Granite Co. 
The lower illustration in this figure relates to a solid insulator for flat-bottomed rails. 

Fig. 216 shows Chambers’ insulator for a rail of tapered channel section, which 
latter has been adopted by the Great Western Railway for their metropolitan lines. 



Protection oj Live Hails. 

A bare exposed 500-volt conducting rail is sometimes required to have some 
mode of protection against anything falling on it and causing short circuits on the 
return rails, and also from the point of view of personal safety to the railway 
company’s servants and of trespassers. Although a potential of 500 volts is rarely 

25i 





ELECTRIC RAILWAY ENGINEERING 


fatal to human life, the fact remains that a few fatal accidents have occurred, of 
which a 500-volt live rail has been the primary cause. Hence there have been many 




Fig. 215. Reconstructed Granite Co.’s Insulators. 

252 





THE DISTRIBUTING SYSTEM 

attempts to effectively guard the conductor rail against wilful tampering and 
accidental contact. 

I ig. 217 illustrates a number of typical methods which have been employed for 
guarding the live rail. The types are indicated by the letters A, B, C, and D, and 
corresponding letters appear in column 4 of 
Table LXAV., thus indicating the methods of 
guarding, employed on several of the roads in 
that table. 

Fig. 217a is the least elaborate, consisting 
of a single board bolted to the rail and raised a 
few inches above it. This method is employed on 
the Mersey Railway, where the live conductors 
are laid adjacent to one another between the two 
tracks. The wooden guard running the entire 
length of the line on each rail has been considered 
sufficient protection to those of the company’s 
servants, who alone have access to the line. 

In Fig. 217b two boards are used, one on 
each side of the rail. These afford better protection 
against anything falling across the line, and 
against the liability of any person coming in 
contact with the rail. 

In Fig. 21/cthe two boards are tapered to more effectively cover in the rail. 

In Fig. 2 1/d an approach is made to covering in the rail with a horizontal board, 
leaving for the collecting shoe a small space between the upper face of the rail and the 
guaid board. 4his necessitates an especially thin projecting shoe. 

In the sketch shown, the cover board is supported by a timber beam on edge, 



Fig. 217. Methods of Protecting Conductor Rails. 



A. ?clt Cushion 
0. Sphinq 

C. lnortTvoc 

D. CeMCK t 

E. 5tcm 


Fig. 216. Chambers’ Patent 
3rd Rail Insulator. 


running beside the rail and bolted thereto. This method is in use on the Paris- 
Orleans line, the New York Subway, and the Wilkesbarre and Hazelton Railroad in 
Pennsylvania. The General Electric Co. of America have used a similar guard board, 
supported on light iron brackets bolted on to the track sleepers. 

The latest development in the direction of completely shielding the conductor rail 

25 3 


























































































2 -S - r» - z-s- 


ELECTRIC RAILWAY ENGINEERING 



is the “ under-contact” method of mounting introduced on 
the lines of the New York Central Railroad Co. Fig. 218 
illustrates the “under-contact” type of rail mounting 
which is being tried on the New York Central Railway. 
The third rail is supported every 11 ft. by iron brackets, 
which hold the insulation blocks by a special clamp. The 
blocks, which are in two pieces, are 6 ins. long, and are 
designed so as to be interchangeable. Experiments are 
still being made with insulators of reconstructed granite, 
vitrified clay, rubber, and indurated fibre, to determine 
the relative advantages of these materials for the existing 
conditions. Between the supporting brackets the upper 
part of the rail is guarded by covering it with wooden 
sheathing, which is built up of three parts nailed together. 
A suitable shoe capable of making contact at its upper or 
lower face can be arranged to pass automatically from this 
rail to the ordinary top-contact rail in portions of the 
track where the latter occurs. 

The advantages claimed for this type are (1) the 
thorough protection of the live rail; (2) less strain on the 
insulators, as the pressure from the shoe acts against 
instead of with gravity; (8) the board protection has a 
continuous support, and is therefore less liable to crack 
or warp; (4) the rail is more protected from the weather 
and hence less liable to corrode ; (5) the contact surface is 
better protected from sleet or snow; (6) it is self-cleaning; 
and as there is much more space between the under-side 
of the rail and the earth, there will be less danger of 
accumulation of snow and ice and rubbish, and therefore 
less leakage. 

The New York Central Railway third rail is not 
mounted rigidly in the insulators but is given a little play 
for expansion and contraction, except at certain central 
points where it is anchored. It weighs 70 lbs. per yard, is 
of special section and composition, and has a resistance 
between seven and eight times that of copper. 

Another type of “ under-contact ” arrangement, 
exploited by the Farnham Co., of Chicago, is illustrated 
in Fig. 219. 


Position of the Conductor Rails. 

There appears to he but little uniformity in deter¬ 
mining the position of the conductor rail with reference to 
the track rails, not only as to the distance between 
conductor rail and track rail, but also as to whether the 
conductor rail shall be between the track rails, in the 
6-foot way, or outside the track on the off-side of the line, 
254 










































THE DISTRIBUTING SYSTEM 

and also as to whether the track sleepers shall carry the conductor rails. The late 
Mr. VV. -h. Langdon, m a paper read before the Engineering Conference in 1903 1 
considered that the conductor rails should be confined to the 6-foot way and 
c issociated entirely from the sleepers which carry the track rails. This view was 
based on the followmg considerations(1) The permanent way must be constantly 
pa lolled , (2) packing and drainage of sleepers and renewals of broken chairs, sleepers 
and rails are constantly necessary, and must be provided for; (3) the off-side of the 
me is almost invariably used for laying out stores for works on the line, and by 
workmen when walking along the line. These considerations would apply more to 
main line railways than to mterurban lines or tubes, and it is notable that the 
Metropolitan and District Railways of London have laid the positive rail on the off¬ 
side of the line outside the track, and the negative midway between the track rails. 
Loth positive and negative rails are mounted on the track sleepers. The distance to 
be employed between the conductor rail and the track rails and the elevation of the 
ormer above the latter depend on the collecting arrangements on the trains, and on 


Body of Car 



the overall width of the rolling stock. In the case of roads carrying also steam traffic, 
the dimensions of the locomotives must be considered in this connection. 

In Table LXX\., we have set forth these dimensions for a number of lines at 
present in operation. While the dimensions are usually of much the same general 
order, there is no evidence of adherence to any standard dimensions. 

At the Engineering Conference in 1903, it was stated that the Clearing House 
Confeience had decided in favour of a distance of 3 ft. II 2 ins. from centre of conductor 
rail to centre of track {i.e., 29£ ins. from centre of conductor rail to gauge line on 
nearest track rail), and that the top of the conductor rail should be 3 ins. higher 
than the top of the track rails. In America a move in the direction of standard 
dimensions has been made in the case of the electrification of the Long Island Rail¬ 
way, 2 where the same dimensions have been adopted as on the Pennsylvania Railway 
and the Interborough Rapid Transit Co.’s lines, namely 27 ins. from conductor rail 
centre to gauge line of track and 3^ ins. difference in height between top of con¬ 
ductor rail and top of track rails. 

1 See Electrician, Yol. LI., p. 447 (July 3rd, 1903). 

2 See Street Railway Journal, Yol. XXVI., p. 828 (Nov. 4th, 1905). 

255 






























ELECTRIC RAILWAY ENGINEERING 

Table LXXV. 


Particulars of Conductor Pails for Various Railways. 




O ^ 

O S' 

1 

O §r>.M 

O a '2 

*5 —< 

Ogy 
§ § 

CD | 


60 * 

G bp 

A- 

bC . 

C bD 

"o ^ 

*M f-l 

°OH • 

P £ <13 

a ~ 0 

~ O 

O *•- «c 

0 0 2 

fc I 

tn 

B. 

JRailway. 

t- <*> 

P 03 

O cc 

r- '-Z 

e 03 

«*-tx 

0 a 

-D3 <D 

P xS 

£i« 02 

O g 

13 £ C 

— '3 ^ _T 

°r- C 

O ® <x> 

^ 03 

o*S £ 

<*-> •—•'A 

0 03 _r 
^ O cS 

c2 

bo 


03 1 —1 

T5 J-t 

O O 

cc — 

0 0 

g - 
H 0 a; 

0 cJ 

0 ^ (X 
-g es 

o 

0 


53 « * 

a> 2 

% ^ 

+3 % 

03 5 

x B ^ 

a " 

0 

§*s 


Main line railways:— 






1 

Albany and Hudson Railway, New York 

— 

— 

27 


6 

2 

Baltimore and Ohio, new location 

— 

— 

30 

— 

31 

If 

3 

,, ,, ,, old location 

— 

— 

24 

— 

4 

Mersey Railway. 

— 

— 

22 

— 

44 

5 

Milan Varese ...... 

A 

D 

26 

a 

7H 

6 

Neuchatel (Fribourg-Morat) 

A 

C 

— 

a 


7 

North-Eastern ...... 

A 

B 

19i 

a 

3j 

8 

New York, New Haven, and Hartford . 

— 

— 

28 j 

b 

n 

9 

Paris-Orleans ...... 

Interurban railways :— 

C 

D 

25f 

a 

7 ? 

*8 

10 

Aurora, Elgin, and Chicago .... 

— 

— 

20J 

— 

6 A 

11 

Columbus, Buckeye Lake, and Newark 

— 

— 

27 

— 

6 

12 

Columbus, London, and Springfield 

— 

— 

27 

— 

6 

13 

General Electric Railway, Schenectady 

— 

— 

28 

— 

3 

14 

Grand Haven, Grand Rapids, and Muskegon 

— 

— 

20| 

— 

6 

15 

Lackawanna and Wyoming Valley 

— 

— 

20^ 

— 

6 

16 

New York Central ..... 

— 

— 

29“ 

a 

2f 

17 

Wilkesbarre and Hazleton Railway 
Underground and elevated :— 

A 

D 

28 

a 

5 

18 

Baker Street and Waterloo .... 

E 

f 

16 (+ ve) 
28i(-ve) 
14f 

a 

3 

1 

b 

H 

19 

Berlin Overhead and Underground 

B 


a 


20 

Boston Elevated ...... 

— 

_ 

20| 

a 

6 

21 

Brooklyn Elevated ..... 

— 

_ 

22 


6 

22 

Central London ...... 

D 

— 

28j 

b 

11 

23 

Great Northern and City .... 

A 

1 

\ 

(+ ve) 

( - ve) 

a 

a 

— 

24 

King’s County Elevated Railway, New York 

— 

— 

19i 


54 

25 

Lake Street Elevated, Chicago 

— 

— 

201 


64 

26 

Liverpool Overhead Railway 

— 

— 

28J 

a 

l| 

27 

Manhattan Elevated ..... 

A 

B 

20| 

a 

n 

28 

Metropolitan District ..... 

A 

AandB j 

16 (+ ve) 
281 (~ ve) 
20i 

a 

b 

3 

11 

29 

Metropolitan West Side Elevated, Chicago . 

C 

— 

a 

6j 

30 

North-Western Elevated Railway, Chicago . 

C 

— 

20^ 

a 

6 i 

31 

Paris Metropolitan ..... 

A 

— 


a 

nqf 

32 

Rapid Transit Subway, New York 

— 

— 

22 

_ 

4| 

33 

South Side Elevated, Chicago 

C 

— 

201 

a 

6j 

34 

Waterloo and City ..... 

— 

— 

28j 

a 

( same 
( level 


From Table LXXA T . we see that several American roads have used 20£ ins. and 
^2 Gi these dimensions. T\ hile there have, in various quarters, appeared sporadic 
attempts to standardise the position of the conductor rail, there appears to be no 
geneial and conceited eftoit for standardisation. A e have given data for as many 
lines as possible, and would not at present lay down any one set of recommendations 
to be followed. It might be convenient to adopt the distance of 28? ins. between 
centre of third rail and gauge line which has been employed by the Underground 

256 








































North Eastern Railed 






20. — Sections op Single Track on Various Railways. 
































































































































10. f). Berlin Elevated <s Underground Railway -Section oj Elevated Brack 


THE DISTRIBUTING SYSTEM 



s 


221. Sections of Double Track on Various Railways. 








































































































































ELECTRIC RAILWAY ENGINEERING 


Railways Co. of London, as this dimension bears some relation to the track gauge, 
being, in fact, exactly one half of the standard gauge of 4 ft. 8^ ins. 

In Fig. 220 are shown sections through the conductor rails and track rails 
for single tracks, and in Fig. 221 for double tracks, of a number of typical railways, 
including most of the types of rail and of constructions which are as yet met with. 

From these figures one may study the various methods of mounting track and 
conductor rails of various sections, and the relative position of the rails on these 
lines, and also in some cases the current collecting arrangements for rails protected 
in the various ways already enumerated. 

In Table LXXIV. we have given for a number of railways, the leading particulars 
of the conductor rails. These comprise length per rail, weight per yard, area of 







Fig. 222. Sections of various Types of Conductor and Track Rails in Common Use. 

(See reference letters in col. A, Tables 75, 103). 

cross-section, and shape of rail section. For the latter item we show in Fig. 222 the 
sections of the various rails in common use, each section being designated with a 
letter, A, B, C, etc., corresponding with the letters in column 5 of Table LXXIY. 

OVERHEAD SYSTEM. 

In the overhead system the conductor is suspended above the track by attachment 
to one or two steel or bronze cables according to the distance between the supports 
and the nature of the train service. The method of suspending the conductor for 
railways, differs from that adopted for tramways. In the latter case the wire or 
conductor is attached to ears fixed to brackets or span wires 100 to 120 ft. apart; this 
method is quite unsuitable for railways owing to the higher speed and voltage 
commonly employed. Height and alignment should be maintained as uniformly as 
possible, so as to prevent shocks to the collector and suspensions, and to avoid 

258 


























THE DISTRIBUTING SYSTEM 

swaying. Further, it is necessary to secure the conductor so as to obviate the risk of 
breakdown, and to secure immunity from contact between conductors and vehicles 
shoukl a conductor break. All these objects are secured by supporting the conductor 
at nequent intervals from steel or bronze cables suspended over the track, thus 
lelieving the conductor of mechanical stresses. 

The suspension cables may be supported from bracket arms attached to side poles 
m the case of a single line, or may be supported from a gantry spanning the tracks 
where two or more tracks are used. 

Yheie side poles are used, the distance between poles on straight lengths of track 
should not exceed 120 ft., and in the case of gantries the distance may be from 120 
to 300 ft., according to the height and strength of the gantry structure. On curves 
of less than 15 chains radius, intermediate poles are necessary for pull-off purposes. 

The supports for carrying the brackets or gantries must be erected so that there 
shall be a minimum clearance of 2 ft. 4 ins. between the structure and the railway 
carriage, in accordance with the Board of Trade rules. 

llie suspension cables should be stranded, and may be of galvanised steel or 
silicon bronze. 

For spans up to 180 ft. a single suspension cable may be used; a steel cable 
made up of 19 strands of No. 12 S.W.G., and having an ultimate tensile strength of 
96,500 lbs. per square inch, will be found suitable. In order to minimize the swaying 

of the suspension cable due to wind pressure, the conductor should be stayed at the 
main supports. 

For spans exceeding 180 ft. in length, a double cable suspension is recommended 
by some, in order to provide against lateral movement or swaying. This object is 
attained by spreading the cables apart from the middle of the span to the supports, so 
that the cables are curved in plan as well as in elevation ; in other words, the cables 
instead of hanging in a vertical plane, are set in an .inclined plane passing through 
the points of support and the conductor hangers; this form of suspension is very 
unyielding as regards lateral movement, but yields slightly to an upward pressure 
and relieves the collector of any shocks. A suitable size and quality of cable for 
double suspension, consists of 7 galvanised steel wires, each No. 10 S.W.G., the material 
having an ultimate tensile strength of 96,500 lbs. per sq. in. 

For single cable suspension, the conductor may be suspended by hangers consisting 
of a single wire of galvanised steel of No. 8 S.W.G., one end being fixed to a clamp on 
the cable and the other to a mechanical ear which grips the conductor. 

Where double cable suspension is used, the conductor is attached to the two cables 
by 10( ^ s Miich may be made adjustable to suit any position in the span, or they may 
be made in fixed lengths, the number of different lengths depending upon the number 
of suspensions in the span. The simplest form of suspension consists of a stranded 
steel wue, the two ends of which are twisted around the suspension cables, the wire 
being passed through an eye in the ear or conductor grip. A suitable size of suspension 
consists of seven strands of No. 14 S.W.G. galvanised steel wire. Where attached to the 
cable, the core is cut away and the two sets of three strands are twisted around the 
cable in opposite directions. The two suspension cables may or may not be tied 
togethei, and eithei a lod or a stranded wire may be used for the purpose. 

In erecting the overhead structure, the cables should be set so that the conductor 
suspended from them is approximately level for mean temperature conditions which 
may be taken at 50 degrees F. in this country. Table LXXYI. gives the dips 
at different temperatures and for spans varying between 120 ft. and 180 ft. for a 

259 s 2 


ELECTRIC RAILWAY ENGINEERING 


single 19/12 steel cable carrying No. 4/0 hard drawn copper conductor, and also the 
dips for a span of 300 ft. for two steel cables, each cable being made up of seven 
No. 10 S.W.G. wires and supporting a No. 4/0 hard drawn copper wire. In each case the 
ultimate strength is taken at 96,500 lbs., and the factor of safety at 4 with wind 
pressure of 80 lbs. per sq. ft. The suspension cables being metallically connected 
to the conductor, are in consequence charged to the same potential, and must therefore 
be insulated from the supports; various forms of insulators are used by different 
companies, some of which will be illustrated later. The suspension cables should be 
clamped down to the insulators. 


TABLE LXXVI. 

Table of Span and Dip of Suspension Cables. 

Breaking stress = 96,500 lbs. per sq. in. = 43 tons per sq. in. 

Modulus of E. = 30,000,000. 

Coeff. of expansion = 000000683 per degree F. 

Factor of safety at 10 degrees F. wind pressure 30 lbs. per sq. ft. = 4. 

Conductor = 4/0 S.W.G. copper. 

Sag in feet for various spans and temperatures. 

Single suspension of 19/12 S.W.G. steel wire cable. 

Weight of span, including suspension cable, hangers and conductor = L2 lbs. 
per foot. 


Span in feet. 

10 

20 

30 

40 

50 

60 

70 

so 

90 

100 

0 F. 

120 

0-86 

0-94 

1-03 

1-12 

1-22 

1-31 

1-40 

1*49 

1-58 

1-67 


130 

1-01 

1-10 

1-20 

1-29 

1-38 

1-48 

1-58 

1-67 

1-77 

1-87 


140 

1-17 

1-27 

1-37 

1-47 

1-57 

1-67 

1-78 

1-88 

1-98 

2-08 


150 

1-35 

1-46 

1-56 

1-67 

1-77 

1-87 

1-98 

2-09 

2-20 

2-30 


160 

1-53 

1-65 

1-76 

1-87 

1-98 

2-09 

2-20 

2-31 

2-42 

2-53 


170 

1-73 

1-85 

1-97 

2-08 

2-20 

2-31 

2-43 

2-55 

2-67 

2-78 


180 

1-94 

2-07 

2-19 

2-31 

2-43 

2-55 

2-69 

2-81 

2-93 

3-06 



Double suspension of 7/10 s.w.G. steel wire cable. 

Weight of suspension cables, hangers and conductor = 1*5 lbs. per foot. 


300 

5-7 

5-83 

5-95 

6-08 

6-21 

6-33 

6-44 

6 - 56 

6-68 

6-8 



The conductor is, as a rule, made of copper and grooved, and the usual size is 
No. 3/0 or No. 4/0 B. & S.; it should be suspended at a height of from 19 ft. to 21 ft. 
above the rails wherever permissible. The conductor is attached to the suspension 
cables by the hangers, at intervals of 10 ft.; where bow collectors are used the 
conductor should be set with a total stagger of 17 ins., that is, 8J ins. on each side of 
the centre. 

On curves of more than 30 chains radius, and with an allowable deviation from 
the central position of 1 ft., no special appliances are necessary ; on curves 
between 15 and 30 chains the conductor may be pulled off from the gantries or side 

260 










































THE DISTRIBUTING SYSTEM 

poles, whilst on curves of less than 15 chains radius, pull-offs must be made to special 
poles provided for that purpose. 

With regard to turnouts and crossways the angles are usually so small that 
special frogs are not necessary ; the frog ear is arranged so that one trolley wire 
passes immediately over the other at the crossing, and the two are brought to the 
same level within a few feet of the crossing, the length of bow being sufficient to 
bridge the two wires before the difference in level affects the contact. In addition to 
the section insulators provided for separating the portions of the conductor fed by 
different feeders, section insulators should be fixed at crossover roads for keeping 
the overhead system of the two tracks entirely separate from one another. 

Ihe overhead work at bridges and tunnels will vary with the type and clearance. 



iig. 22o. Photogrape showing Single Cable Suspension with Side Poles as 

ERECTED BY THE WESTINGHOUSE COMPANY. 

At high biidges it may be possible to carry the overhead wires through without 
special woik. Where the clearance is small, it will be necessary to support the 
conductor from insulators attached directly to the structure. 

Wlieie, however, the clearance is so small as not to admit of this arrangement 
with any degree of safety, the conductors should be spread out of reach of the bow, 
and additional dead wires fixed to provide a running surface for the bow, section 
insulators being provided at the necessary distance apart on each side of the bridge so 
that the portion under the bridge cannot, under any circumstances, be made alive. 
This arrangement is not suitable for tunnels where a continuous live conductor must 
be provided ; in this case the conductor must be fixed near the ground at the side of 
or between the rails, and the current collected by shoes attached to the cars; for the 
safety of the men working on the line, this arrangement will necessitate a reduction 

261 







ELECTRIC RAILWAY ENGINEERING 


of the voltage of supply from that given by the overhead conductors to that needed 
directly at the motor terminals, the car transformer being cut out of circuit whilst 
running over this section. 

We now submit illustrations of finished structures and also details of parts of the 
overhead structure. 

A photograph of a side pole construction with single cable suspension is shown in 



Fig. 224. Photograph showing Double Cable Suspension Supported 
from Gantries constructed by the Westinghouse Company. 

Fig. 223, and a photograph of a double suspension with gantry supports is shown in 
Fig. 224. 

As regards the details of construction of overhead conductor and supports, 
Fig. 225 shows a side pole and bracket for single cable suspension and single 
insulation, consisting of a latticed post with angle iron bracket arm carrying a 
porcelain insulator to which the suspension cable is clipped; the conductor is stayed 
from the post by means of a specially prepared rod of hickory. 

262 



















THE DISTRIBUTING SYSTEM 

Fig. 226 shows a side pole and bracket for single cable suspension, but with 
double insulation with special form of anchorage designed to yield slightly in a 
vertical direction, so as to prevent shock as the collector passes, and at the same time 




Fig. 225. Side Pole Single Insulation, Single Cable Suspension. (British Thomson- 

Houston Co.) 


to effectively prevent swaying in a lateral direction ; these methods are used by the 
British Thomson Houston Co. 

Fig. 227 shows the method adopted by the Westinghouse Co. for suspending 
and staying the conductor for single suspension, single insulation with side 
poles. The insulator, h ig. 228, consists of a corrugated porcelain cylinder about 
6 ins. long, 6 ins. diameter, with a 8 in. hole and a groove about half-inch deep about 
its centre. This porcelain is cemented on a malleable iron sleeve fitted with clamps, 

263 



















































































































ELECTRIC RAILWAY ENGINEERING 


by means of which it is secured to the bracket arm. The clamps of the mounting 
sleeve are provided with lugs into which loops are inserted for the purpose of 




Fig. 226. Side Pole Double Insulation Single Cable Suspension with Vertically 
Yielding Anchorage. (British Thomson-Houston Co.) 

protecting the porcelain against accidental breakage by reason of a trolley Hying off 
the wire and striking the porcelain. 

Fig. 229 shows the stay used to prevent the conductor from swaying. 

Fig. 230 shows a section insulator; as the suspension cable and the conductor are 
electrically connected it is necessary to break the circuit on both. The ends of the 
suspension cable are fastened to separate line insulators which are suspended from 

264 










































































































THE DISTRIBUTING SYSTEM 

the bracket arms, and the continuity of the conductor is broken and the space filled 
by a piece of specially treated hickory. 

Fig. '231 shows another method of sectionalising the conductor: the ends of the 



Fig. 227. Side Pole and Bracket Arm, with Insulators and Stay. 

(British Westinghouse Co.) 



two sections, instead of being continued in a straight line, run parallel for a short 
distance, the bow being long 
enough to bridge the space 
between them; oil break switches 
are also shown for connecting up 
the sections, and an air break 
switch for connecting the con¬ 
ductors over the separate lines 
of track. 

Fig. 232 illustrates the hanger 
for suspending the conductor from 
the cable ; the upper end of the 
hanger is clamped to the cable 
and the lower end carries a vice 
which grips the conductor, the 
latter being grooved to afford a 
hold for the clips. 

Fig. 233 shows a curve pull Fig. 228 .—Bracket Arm Insulator. 
off; on sharp curves these must Westinghouse Co.) 


(British 


265 

































ELECTRIC RAILWAY ENGINEERING 


be provided in order to maintain the position of the conductor relative to the 
track, within the prescribed limits. 

For two or more tracks, it is necessary to employ a gantry spanning the tracks 
for supporting the overhead lines; these may be of light design where they are spaced 
from 150 to 180 ft. apart, in which case a single cable suspension is used. Fig. 234 



Fig. 229. Insulated Stay for Trolley Wire for Attaching to 
Bracket Arm. (British Westinghouse Co.) 


shows a gantry for two tracks, supporting two conductors on the single cable principle 
with double insulation. In many cases it is found cheaper to increase the length of 
span and diminish the number of supports ; in this case the gantry supports are 
stiffer and higher, and it becomes necessary to employ a double cable suspension to 
prevent lateral movement of the conductor. 

A general view of this kind of structure is shown in Fig. 235. The span 



Fig. 230. Section Insulator. (British Westinghouse Co.) 

is 300 ft. Fig. 235 shows gantry constructions for two, four and six tracks with 
double cable suspension. The two supporting cables and the conductor are tied 
together, the ties forming three sides of a triangle; the cables are set in a plane 
passing through the points of suspension and the attachment to the conductor, this 
forming a very rigid arrangement; the triangles formed by the tie rods remain 

266 










THE DISTRIBUTING SYSTEM 


similar, but vary in size according to their position in the span. The ties can be 
made in sets and non-adjustable, or in single adjustable pattern. 

TRACK RAILS. 

The track rails are frequently used as a return conductor, and it is important, 
therefore, to know the properties of track rails as conductors of electricity and the 
methods adopted for securing electrical continuity. 



267 















































































































































Fig. 232. Hanger of Suspender. (British Westinghouse Co.) 




Fig. 233. Curve Pull-oee. (British Westinghouse Co.) 



Fig. 234. Gantry for Two Tracks, Supporting Two Conductors on the Single Cable 
Principle with Double Insulation. (British Thomson-Houston Co.) 

268 

















































































































Fig. 235 . Gantry Constructions for Two, Four, and Six Tracks, with Double Cable Suspension. 





















































































































































































































































- 















































































































THE DISTRIBUTING SYSTEM 


M ere the electrical standpoint alone considered, the material of the track rails 
should be chosen with reference to its specific conductivity. This is, of course, 
impracticable, as a minimum of wear is a matter of prime importance. 

The most extensively employed material for track rails is hard steel, but practice 
as regards the composition of rails has varied considerably in the past, and even now 
one finds wide variations in the practice of different railroads and of different countries. 
It may be said that English rails some years back commonly conformed to the following 
analysis:— 


Carbon . 
Manganese . 
Silicon . 
Phosphorus . 
Sulphur 


0-25 to 0-35 
0-8 to 1-0 
0-05 
0-06 
0-06 


Of late 
specifies— 


years the percentage of cai 


bon has increased. 


One large railway company 


Carbon 
Manganese . 
Silicon 


0-4 to 0-5 
0-85 to 095 
0-06 to 0-10 


Phosphorus. 
Sulphur 


0-08 to 0-1 
0-08 


In American practice, the carbon runs still higher, and may be fairly represented 
by the following analysis:— 


Carbon 
Manganese . 
Silicon 
Phosphorus 
Sulphur 


0-45 to 0 55 
0'8 to 1-0 
Ol to 0'15 
0-06 
0-06 


A report recently issued by the American Society of Civil Engineers, drawn up 
after the investigation of manufacture and chemical composition of rails, recommends 
the following specifications :— 


Bessemer Steel Bails. 


Composition. 

70 to 79 lbs. 

Per cent. 

SO to 89 lbs. 

Per cent. 

90 to 100 lbs. 
Per cent. 

Carbon ..... 

050 to 0-60 

0-53 to 0-63 

0-55 to 0-65 

Phosphorus, not exceeding 

0-085 

0-085 

0-085 

Silicon 

0-20 

0-20 

0-20 

Sulphur 

0-075 

0-075 

0-075 

Manganese .... 

0-75 to 1-00 

0-80 to 105 

0-80 to 1-05 


Basic Open-hearth. 


— 

70 to 79 lbs. 

Per cent. 

80 to 89 lbs. 

Per cent. 

90 to 100 lbs. 

Per cent. 

Carbon ..... 

0-53 to 0-63 

0-58 to 0-68 

0 65 to 0-75 

Phosphorus, not exceeding 

0-05 

0-05 

0-05 

Silicon ,, 

0-20 

0-20 

0-20 

Sulphur ,, 

006 

0-06 

0-06 

Manganese .... 

0-75 to 1-00 

0-80 to 1-05 

0-80 to 1-05 


269 

































ELECTRIC RAILWAY ENGINEERING 


The manufacturers’ standard specification for the acid Bessemer process has been 
as follows:— 


Composition. 

70 lbs. up to SO lbs. 
Per cent. 

80 lbs. up to 90 lbs. 
Per cent. 

90 lbs. up to 100 lbs. 
Per cent. 

Carbon ..... 

0-45 to 0-55 

0-48 to 0-58 

0-50 to 0-60 

Phosphorus, not exceeding 

o-io 

o-io 

o-io 

Silicon ,, 

0-20 

0-20 

0-20 

Manganese .... 

0-75 to 1-00 

0-80 to 1-10 

0-80 to 1-10 


In France, yet higher percentages of carbon have been employed, running up to 
nearly 1 per cent. 

The bull-head rail has now been standardised in Great Britain by the Engineering 



SIS 

<9 



Fig-. 236. —Engineering Standards. 


100 lbs. per yd. 
Committee Standard Sections. 


Standards Committee. Three standard sections, 
100 lbs. per yard, are shown in Fig. 236. 

Whether of Bessemer or Siemens-Martin 
specified as follows :— 

Carbon ...... 

Manganese ..... 

Silicon not to exceed 
Phosphorus ..... 

Sulphur ...... 


weighing respectively, 80, 90, and 

steel, the chemical composition is 

0-35 to 0-5 per cent. 

0-7 to 1-0 

o-i 

0'075 ,, 

0-08 


The results, as far as regards the electrical resistance, are shown in the following 
table 1 of trials of sample sections of steel rail of varying composition, which were 
furnished for testing purposes :— 


Carbon. 

Manganese. 

Silicon. 

Phosphorus. 

Sulphur. 

Resistance in Ohms 
compared with 
Copper at 20° C. 

Resistance in Ohms 
of 1 Mile, 1 Square 
Inch Section at 20° C. 

0-378 

0-550 

0-181 

0-040 

0041 

10-8 

0-468 

0-446 

0-568 

0-188 

0-046 

0-044 

11-1 

0-482 

0-536 

0-592 

0-201 

0-051 

0-059 

11-3 

0-490 

0-568 

0-608 

0-204 

0-053 

0-061 

11-4 

0-495 

0-588 

0-632 

0-214 

0-056 

0-065 

11-5 

0-499 

0-610 

0-650 

0-220 

0-062 

0-071 

12-9 

0-560 


1 These results, as also certain others contained in this section, are taken from a paper entitled 
“Earth Returns for Electric Tramways,” by H. F. Parshall.—“Journal of the Institution of Electrical 
Engineers,” Yol. XXVII., p. 440. 


270 


























































THE DISTRIBUTING SYSTEM 

Eight i b-lb. track rails, tested in place after two and a half years’ use, gave the 
following results: — 


Test Number. 

Resistance compared 
with Copper at 20° C. 

Resistance in Ohms, of 
1 Mile of 1 Square Inch 
Sectional Area at 20° C. 

1 

11*3 

0-490 

2 

10-3 

0-447 

3 

10-1 

0-438 

4 

10-7 

0-464 

5 

9-65 

0-419 

6 

10-07 

0-437 

7 

10-25 

0-445 

8 

10-50 

0-455 

Average 

10-4 

•45 


Two old 65-lb. rails, much worn, tested in places, gave the following results :— 


Test Number. 

Resistance compared 
with Copper at 20° C. 

Resistance in Ohms of 

I Mile of 1 Square Inch 
Sectional Area at 20° C. 

1 

11-7 

0-508 

2 

12-3 

0-534 

Average 

12-0 

0-52 


Higher values would he expected owing to the wearing of the rail, which is not 
allowed for in the calculations. 

Two new 90-lb. rails, tested in place, gave the results following:— 


Test Number. 

Resistance compared 
with Copper at 20° C. 

Resistance in Ohms of 

1 Mile of 1 Square Inch 
Sectional Area at 20° C. 

1 

10-6 

0*460 

2 

10-4 

0-451 

Average 

10-5 

0-455 

lot laid, gave 

results as follows :— 

1 

io-o 

0-434 


Thus for practical purposes, we may estimate the resistance of track rails on the 
basis of a specific resistance equal to eleven times that of copper 

In Table LXXVII. are given for the three standard rails of Fig. 236, the resistances 
in ohms per mile for single track and two-track roads, the resistance of the bonds being 

271 




































ELECTRIC RAILWAY ENGINEERING 


assumed as negligible. For types of bonding where this assumption should not hold, 
suitable correction factors are employed based on experience. A. poorly bonded track 
may have a far higher resistance. The table also includes the tons per mile, and also 
the cost of the steel rails per mile of single and double track. 

The figures given in Table LXXVII. are based on the assumption that the rail 
has Kko times the resistance of pure copper. 


Table LXXVII. 

Particulars of Standard Track Rails. 



Sin 

gle Track—Two Rails. 

Double Track 

—Four Rails. 

Weight of Rail 
in Pounds 
per Yard. 

Weight of Rails 
in Tons per Mile 
of Track. 

Resistance of 
Track in Ohms 
per Mile. 

Cost of Track 
Rails in Pounds 
per Mile. 

Weight of Rails 
in Tons per Mile 
of Track. 

Resistance of 
Track in Ohms 
per Mile. 

80 

126 

0-028 

660 

252 

0-014 

90 

141 

0-025 

742 

282 

0-0125 

100 

157 

0-0225 

825 

314 

0-0112 


Specific resistance of steel = 105 times that of pure copper. 


In Table LXXYIII. are brought together a considerable number of particulars 
of the track rails of various electric railways. 


Table LXXYIII. 

Particidars of Track Rails of Various Railways. 


Particulars of Track Rails. 


Railway. 


1 

2 

3 

4 

5 

6 

7 

8 
9 


Paris Metropolitan 
New York Subway 
Boston Elevated . . . . 

Central London ... 

Great Northern and City Railway 
Lancashire and Yorkshire Railway 
Berlin Electric Overhead and 1 
Underground ) 

Berlin-Zossen . 

Yaltellina . 


10 

11 


12 


13 

14 


City* and South London 


Baker Street and Waterloo f 
Railway ( 

Petaluma and Santa Rosa Rail- | 
way, California / 

Milan - Varese - Porto Ceresio ) 
Railway, Italy j 

St. Georges de Commires la ) 
Mure, France j 


Length in 

Weight in 

Section. 

Area in Square 

Feet. 

per Yard. 

(See Fig. 222.) 

Inches. 

50 

100 

A 

9-8 

33 

100 

A 

9-8 

60 

85 

— 

8-36 

60 (B) 

100 (B) 

B used for points 

9-8 

60 (C) 

100 (C) 

C used in tunnels 

9-8 

— 

85 

Flanged cross-section 

8-36 

— 

70 

B 

6-9 

39 ft. 4 ins. 

( 52 

[ 86 

A 52-lb. rails west side 
A 86-lb. rails east side 

5-12 

8-46 

39 ft. 5 ins. 

82 

A 

8-06 


( 55 

— 

5-41 


/ 71 

— 

7-0 


( 60 

— 

5-9 


/ 80 

— 

7-87 

34 ft. 11 ins. 

90 

B 

8-85 

36 ft. 5 ins. 

90 

B 

8-85 

30 

70 < 

A American Society Civil 

1 fi-Q 

Engineers’ standard 


— 

72-6 

A 

7-15 

36 

60 

— 

5-9 




































THE DISTRIBUTING SYSTEM 

Table LXX\ III.— continued. 


15 

16 

17 

18 

19 

20 
21 
22 

23 

24 

25 


Railway. 


Liverpool Overhead 
Mersey Railway, Liverpool . 
Manx Electric Railway, Douglas, ( 
Ramsey ‘ i 

Seattle-Tacoma . 

Jackson and Battle Creek Railway 
Manhattan Elevated 
Metropolitan District Railway 
London, Brighton, and South } 
Coast Railway i 

New York Central 
Paris-Versailles . 

North-Eastern 



Particulars of Track Rails. 

Length in 
Feet. 

Weight in 
Pounds 
per Yard. 

Section. 


56 

A 

36 

86 

B 


56 

A 


62-5 

A 

30 

70 

A 

30 

70 

_ 

A 


— 

— 


Area in Square 
Inches. 


5- 51 
8-46 
5 *51 

6- 16 
6-9 
6-9 


Bonds. 



Fig. 237. 


General Electric Co. (U.S.A.) 
Rail Bond : Section through Bond, 
showing Effect of Compression. 


“ mTTXlTTY percentage .°f the boncls at present in use are of the so-called 

JT t ?’ PC ’ and C ° nsl5t 111 a l,eav - v «<>PPer "'ire or cable, with drop-forged 

e minals. In some types of bond, cast copper ° 

terminals have been employed, but these 
have been most unsatisfactory. The resist¬ 
ance of cast copper is very much greater 
than that of drawn copper, so that it is not 
so much suited for bonds. Further, and most 
impoitant, the union between cast copper and 
drawn copper wires is imperfect, so that the 
electrical resistance is much higher than that 
between two pieces of bare copper fused 
together. 

,, T 6 P re88u re-contact type of bond, in spite of the greatest care in installing 
there will always be some slight movement between the surface due either to tern’ 
perature changes or to vibration occurring during the passage of cars or trains, or to 
oni nned effect of temperature changes and vibration. This leads ultimately to a 

destroyed. 0 6 ^ ^ ° f ° Xk ' e f °™ S ’ a " d the Va ' Ue of the contact is gradually 

Tire pressure-contact types of bond have been of two kinds. In the one the bond 

two cT T f °f Ce< l U '°, Ugh an yternal cylindrical copper sleeve, but this type requires 
two contact surfaces between the rail and the bond. In an alternative type, a steel 

channel pirns driven through a hole in the head of the bond, forcing the copper bond into 
close contact with the metal rail. » 11ounci into 

e.r.e. 2 y 3 T 


























ELECTRIC RAILWAY ENGINEERING 



One such type of bond, made by the General Electric Co., U.S.A., is shown 


Fig. 238. General Electric Co. Type of Bond, 
Protected by Fishplate. 

In Fig. 239 the bonds are located under 


in Fig. 237, and the steel channel 
pin is shown at its centre, as already 
explained. In this type of bond, 
the conical ends of the steel 
channel pin are hardened, and the 
shank, which is soft at the centre, 
expands under the pressure which 
. is applied at the two ends of the 
bond. 

Fig. 238 shows a bond of this 
type, arranged to be protected by the 
fish-plate. For this purpose it has 
a double cable for straddling the 
fish-plate bolts. 

the bottom flange of the rail. In 



iig. 239. General Electric Co. Ty'pe of Bond under Sole of Rail. 


Fig. 240 there is not room enough for the bonds under the fish-plate, and 
it becomes necessary to locate them outside of the fish-plate. 



Fig. 240. General Electric Co. Bond outside 
Fishplate. 


Fig. 241. Rail Bonding! Press. 



274 











THE DISTRIBUTING SYSTEM 

Fig. 241 shows a rail bond compressor used for expanding the bond in place. 

The Piotected Rail Bond, made by the Forest City Electrical Co., is an instance 



of another frequently used type of bond. Fig. 242 shows the general arrangement 
of a joint with protected bonds between the fish-plate and the rail web. The bond 

275 T 2 













































































































































































































ELECTRIC RAILWAY ENGINEERING 

consists of copper strips or stranded copper, fused or welded on to solid cylindrical 

terminals, which are expanded into 
holes in the rail by a bond com¬ 
pressor. Fig. 243 gives a view of 
this bond with fish-plate removed. 
The Forest City bonds are used 
on the Metropolitan District 
Railway Co.’s track. Figs. 244 
and 245 show one of these quad¬ 
ruple bonds located beneath the 
sole of the rail. 

Fig. 246 shows the Chicago Rail Bond, in which contact is made by pressure of a 



Fig. 243. 


Protected Type Rail Bond under' 
Fishplate. 



Fig. 244. 


Protected Type of Bonds on London Underground Electric Railways. 




copper cylinder against the sides of a hole in the rail by means of a steel pin driven 

into the hole in the copper cylinder. This 
makes a solid contact between the iron and 
the copper, excluding moisture and air and 
minimising corrosion. With the original 
Chicago bond, as illustrated in Fig. 246, it 
was necessary for both sides of the rail to be 
exposed, as the pin was driven in from the 
reverse side of the rail to that on which the 
bond was placed. This led to the develop¬ 
ment of the Chicago Crown Bond, illustrated 
in Fig. 247, in which the copper terminal is 
made so that the securing pin is driven in 

Fig. 245. Protected Type of Bond on from the same side of the rail as the bond. 
London Underground Electric Railways. The connecting piece is either of solid oi 

276 
































































































































































THE DISTRIBUTING SYSTEM 



Q Q | 

€>> 

#1 



A rpi_rm_ 

! IT'D- 


I 

T 

| 

1 

1 

£ 

40) <gr- 

w 


Fig. 246. 


Chicago Rail Bond. 


stranded copper, welded into the copper terminal cylinders, the stranded form 
allowing greater flexibility. 

Crown bonds are employed on the Central London Railway and elsewhere. 

The Neptune Bond has a steel cylindrical pin driven into a cylindrical 
hole in the copper terminal, which 
fits a hole in the web of the 
rail. 

The Columbia Bond (Fig. 248) 
is another type where direct 
pressure between the copper ter¬ 
minal with the sides of a hole in 
the web of the rail, is used. In 
this case the bond end takes the 
form of a tapered cylinder on 
which is slipped from the other 
side of the rail, a tapered thimble. 

The copper terminal and thimble 
are expanded by a hand press 
to give a solid contact with 
the rail. 

Amongst the various pressure-contact t} r pes of bond referred to above, there would 
not appear to be much to choose, and all are extensively used at the present time. 
The chief property is to get a solid, durable, and reliable contact between the rail and 

the bond, and generally wherever 

_the bond is pressed and expanded 

into the rail this is obtained. 

It will be noted that, although 
in the pressure-contact type of 
bonding the contacts when new 
may have an absolutely negligible 
resistance, the resistance of the path for the return current is increased by the 
resistance due to the length of the bond itself. For this reason it is desirable to 
make such bonds as short as possible. On the other hand, the shorter the bond 
the less is its flexibility and the greater is the liability to deterioration, and, as a 
matter of fact, fairly long bonds are used 
for this more important reason. In newly 
and correctly bonded roads, the resistance 
of the bonded rail return need rarely be 
more than 5 per cent, greater than that 
due to the rail itself. The deterioration 
of bonding is generally rather rapid ; at 
the end of a few years at the longest, the resistance will in many cases be increased 
to a considerable percentage. These remarks refer to the resistance of the metallic 
circuit on the assumption that no current flows by the earth. As a matter of fact, 
however, large percentages of the current return by the earth, thereby greatly reducing 
the voltage drop. This is liable to lead to undesirable consequences through the 
electrolysis of waterpipes and ironwork in general, located below the street level, 
and Board of Trade regulations have been framed with a view to limiting 
this danger. 

277 





Fig. 247. 


Crown Rail Bond. 





















































ELECTRIC RAILWAY ENGINEERING 

Soldered Hail Bonds. 

In this type of bond, the continuity is made from rail to rail by means of a strip 
or bundle of strips of copper actually soldered on to the rails. 

Tests and inspection after several years’ working on several roads are said to have 
shown the bonds and contacts to be in as good condition as when installed. It is 




Fig. 249. Thomas’ Soldered Rail Bonds. 

stated that the Thomas Bond (Fig. 249) has been in use for over 3 years on the 
Boston Elevated Railway, the Bershore Street Railway, and the Chicago and Milwaukee 
Electric Railway. Fig. 249 will explain the construction of this bond, in which the 



Fig. 250. Shawmut Soldered Rail Bond. 

bond, besides being soldered on to the rails, is pressed against them by the fish-plate 
when bolted on. 

Fig. 250 depicts several types of the Shawmut soldered bond. This bond is 
similar to the Thomas type. The bond is built of flexible copper ribbon, and 
can be fixed on the web, or base, or ball of the rails, or from the web to a 
fish-plate, as shown. 















THE DISTRIBUTING SYSTEM 

Resistance of Bonds. 

Table LXXIX., compiled from tests made by one of the authors, 1 gives some 
data as to the resistance of bonds. 


Table LXXIX. 

Resistances of Rail Bonds. 



Resistance in 
Microhms of Two 
Terminals in Series. 

Resistance of Terminals 
only Single Bonding per 
Mile Single Track. 

Conditions of Bonding. 

|-in. copper bond (4/0) terminals, web 

\ 


( Clean bond, clean 

of rail ^ in. thick, hole in rail 

! 14)7 ) average 

) 173'5 j average 
j 189-5 j 181-5 

| in. in diameter, contact area E37 

| 2-15 j 2-06 

hole, drilled with- 
( out oil, well bonded. 

sq. ins. ...... 

^-in. copper bond (4/0) terminals, same 




as above ...... 

2-50 

220 

Bond well bonded. 

Copper bond, Lin. hole, web of 
rail ^ in. thick, contact area 1-37 
sq. ins. .... . . 

i q.? | average 

( 635 ) . 

835 av “'* ge 

hole drilled with oil. 

Hole clean, well 

(7-7) 8,1 

(680 j 716 J 

bonded. 


Table LXXX., from “ The Engineering and Electric Traction 
(Dawson, 1903), gives further data of bond resistances from tests 


Pocket-book ” 


Table LXXX. 

Comparison of Resistances of various Rail Bonds, not including in any case the 

Resistance of the Rail. 


Test 

Number. 

Kind of Bond. 

Current in 
Amperes. 

Difference of 
Potential in Volts, 

Resistance in 
Ohms. 

1 

One 4/0 plastic copper bond 

1,915 

0-0234 

0-0000122 

2 

Two ,, ,, . . 

1,915 

00127 

0-00000668 

3 

One 6/0 ,, ,, ... 

1,910 

00114 

0-00000593 

4 

Two ,, ,, ... 

1,880 

0-00678 

0-0000036 

5 

One 2/0 copper bond with steel driving pin 

1,610 

0-75 

0-00046 

6 

1 W O j j j) j? 

1.805 

0-278 

0-000154 

7 

One 4/0 flexible copper bond 

1,830 

0-119 

0-000065 


The tests from which the above results were obtained were carried out by the 
Ecole d’Electricite, under the auspices of the French Government, at Paris in July, 
1900. 

Table LXXXI. gives particulars of rail bonds employed on a number of typical 
railways. 

1 “ Earth Returns for Electric Tramways,” H. F. Parshall, Journal Institute Electrical Engineers, 
Yol. XXVII., p. 440. 


27 9 






























ELECTRIC RAILWAY ENGINEERING 

Table LXXXI. 

Particulars of Rail Bonds on various Railtvays. 






Total Cross-section 





of Bonds. 

Railway. 

Number of Bonds 

Build of Bond. 

Name and Manufacturer 



per Joint. 

of Bond. 

Square 

Circular 







Inches. 

Mils. 

Baker Street and Waterloo 

4 

Flexible plaited' 

American Steel and 


_ 



wire 

Wire Co. 



Boston Elevated 

1 

— 

— 

•236 

300,000 

Central London 

( 4 (third rail) 

1 2 (track rail) 

) Flexible plaited 
j wire 

| Chicago Crown J 

■62 

•31 

790,000 

395.000 

City and South London . 

2 

Flexible wire 

— 

•165 

210,000 

Jackson and Battle Creek 

2 

Foot bonds 

— 

•236 

300,000 

Lackawanna and Wyoming 

2 

Foot bonds 

— 

•314 

400,000 

Valley Railway 
Lancashire and Yorkshire 

4 

Semi-flexible 

Forest City Elec- 





copper ribbon 

trical Co. 



Manx Electric Railway . 

— 

Rigid and 

Columbia, Chicago 

— 

— 



flexible bonds 

Crown 



Mersey Railway 

— 

Flexible copper 

Forest City Elec- 

•314 

400,000 


strip 

trical Co. 



Metropolitan and District 

4 

Flexible copper 

Forest City Elec- 

— 

— 


strip 

trical Co. 



Neuchatel 

1 

Flexible copper 

Chicago Crown 

•155 

197,500 



wire 




New York, New Haven, 

2 

Flexible copper 

— 

1-415 

1,800,000 

and Hartford Railway 


strip and cable 




New York Subway . 

( 4 (third rail) 

1 ( 2 (track rail) 

) ( 

j ( 

Mayer and Englund 
Co. 

•943 

•314 

1,200,000 

400,000 

North-Eastern. 

2 

Flexible copper 

Crown Bond. British 

•166 

212,000 



wire 

Thompson-Houston 



Paris Metropolitan . 

4 

Flexible copper 

Chicago Crown 

•316 

402,500 



wire 




Paris-Versailles 

( Third rail 
i ( Track rail 

} 

i 

( 

\ 

•93 

•2325 

1,180,000 

296,000 

Seattle-Tacoma Railway . 

j Third rail 
i Track rail 

\ 

) 

Clarke Bond, by l 
Chase Shawmutt ( 

•59 

•393 

750,000 

500,000 


Resistance of Rails to Alternating Currents. 

In traction by alternating currents, either multi-phase or single-phase, use is 
made of the rails as part of the conducting circuit in order to lessen the amount 
of overhead constructional work. Owing, however, to the greatly increased 
resistance of iron to alternating currents, the use of the rails as a conductor is 
limited to short lengths, the rails being supplemented by a copper conductor, to which 
they are connected at short intervals. The virtual resistance of iron or steel con¬ 
ductors to alternating currents is a somewhat complicated phenomenon ; it varies with 
the periodicity of the currents, the area and form of conductor, and the permeability. 
The latter, again, depends upon the current in the rail; therefore any statements of 
the virtual resistance of iron or steel to alternating currents is not completely 
defined unless all the conditions listed above are specified. 

The resistance referred to here is a true ohmic resistance, which is increased owing 
to the tendency of the currents to keep to the outer layers of the conductor and avoid 
magnetisation of the material, thus limiting the effective area of the material for 
conducting purposes. Combined with the resistance effect is the inductance within 

280 
































THE DISTRIBUTING SYSTEM 

the rail, which tends to diminish as the resistance increases. The total drop on a rail 
is that due to the resistance and inductance, the resultant of which is the impedance. 

The vaiiation in permeability constitutes a difficulty in the predetermination of 
the impedance and its components; the permeability depends on the magnetization, 
which, again, depends upon the current in the rail. The permeability is apparently 
ve U f°i small cunents say, less than 20 amperes per square inch—but increases 
rapidly when the currents are increased. At still higher current values, the 
permeability decreases. 

Owing to the complexity of the phenomenon, impedance values can only he 
obtained by experiments. Experiments were carried out by one of the Authors upon 
the conductor rails of the Central London Railway. These rails were specially rolled 
for high conductivity, viz., 7 times that of copper, and are of channel section, weighing 
80 lbs. to the yard. 

The circuit consisted of two rails, of the quality and form stated above, placed 
14 ft. apart, the length of each rail being 1,695 yds. Alternating currents having 
a periodicity of 25 cycles per second, were passed through the rails, and the following 
results obtained:— 


Current in 

Difference of Potential 

Impedance. 

Amperes. 

in Volts. 

164 

179 

1-09 

180 

200 

1-11 

195 

232 

1-19 


The resistance of the circuit for continuous currents is 0‘0694 ohms, and the 
impedance of the rails, due to the resistance and inductance within the rails, deduced 
from the above readings and taking average values, is 0‘78, or a drop of 11 times that 
for continuous currents; the resistance component is 0‘5, which is 7'2 times the 
resistance to continuous currents. 

Inasmuch as so much depends upon the form of the rail and its magnetic and 
electrical properties, the behaviour of track rails cannot be deduced from these 
readings. A very exhaustive investigation into the electrical and magnetic properties 
of track has been carried out by Prof. Wilson, of King’s College (see Electrician, of 
23rd February, 1906), and determinations were made of the inductance and 
resistance of bull headed rails of standard section and weighing 70 lbs. to the yard, 
also the inductance of a circuit formed of one rail and two rails with an overhead 
conductor placed at different heights. The rails experimented on had a specific 
resistance of 8*45 x 10* 6 per cubic inch, the resistance being 13 times that of copper, 
and presumably the permeability was of low value. Inasmuch as the conductivity, 
permeability and form of section is different, the results differ from the results obtained 
by us as quoted above. 

Measurements of inductance values were made with currents of 50, 100, 150 and 
200 amperes passing through the rail, and at periodicities of 100, 50 and 27 cycles per 
second. The results show how the inductance and resistance varies with current and 
periodicity, also the effect of the mutual action of the currents and the overhead 
conductor. The information obtained is such as to enable values to be obtained for 
different heights and different periodicities. With regard to rails of different sizes, 
Prof. Wilson suggests that a very close criterion of the properties of different sizes of 
the same form and of different forms is obtained from the periphery; this principle 
has been adopted by us in determining the properties of the different rails. 

The following tables have been deduced from Prof. Wilson’s experiments and 

281 


ELECTRIC RAILWAY ENGINEERING 


apply to standard sections of bull headed rails ; for periodicities of 15, 20 and 25 cycles 
per second, the values given are assumed to be constant for different currents. This does 
not hold for large variations, but if we limit the current to 20 amperes per square inch, 
which is a serviceable limit, the variation below this, at the periodicities given, is within 
the limits of the variation of magnetic properties of rail material and within the limits 
of errors in observation. The values given hold for rails of the same specific resistance 
as that experimented on, and inasmuch as the rail was obtained from one of the 
principal railway companies, it is reasonable to assume that it is fairly representative 
as regards its mechanical, magnetic and electrical properties, of the railway rails in 
general use in this country. 

The impedance values given with the Tables take account of the inductance 
within the rail only and represent values which would be obtained were the return 
current carried in a closely fitting tube outside the rail ; when stated in this form the 
values can be applied to calculate the impedance of the circuit with the overhead 
conductor at different heights. 

Table LXXXII. gives resistances, reactances, and impedance per mile of single 
rail for rails of different weights for currents at 25 cycles. 


Table LXXXII. 

Resistance, Reactance and Impedance per mile of Bull Head Rails. Standard Section, 

25 cycles per second. 


Weight of Rail 
lbs. per yard. 

Inductance. 

Reactance. 

Virtual 

Resistance 

(ohms). 

Impedance. 

Resistance 
to Continuous 
Currents 
(ohms). 

Ratio of Drop 
AC/CC 

60 

•00164 

■257 

•170 

•308 

.0925 

3-33 

70 

•00156 

•245 

•162 

•295 

•0792 

3-74 

80 

•00149 

•233 

•155 

•280 

•069 

4-05 

90 

•00142 

•223 

•148 

•267 

•0618 

4-32 

100 

•00136 

•214 

•142 

•257 

•0556 

4-62 

110 

•00131 

•206 

•136 

•247 

•0505 

4-89 


I able LXXX1II. gives the same constants for currents of 20 cycles. 


Table LXXXIII. 

Resistance, Reactance and Impedance per mile of Bull Head Rails. Standard Section, 

20 cycles per second. 


Weight of Rail 
lbs. per yard. 

Inductance. 

Reactance. 

Virtual 

Resistance 

(ohms). 

Impedance. 

Resistance 
to D. C. 
(ohms). 

Ratio of Drop 
AC/CC. 

60 

•00171 

0-215 

0-147 

0-261 

•0925 

2'82 

70 

•00163 

0-205 

0-14 

0-249 

•0792 

3-14 

80 

•00155 

0-197 

0-134 

0-24 

•069 

3-47 

90 

•00149 

0-187 

0-128 

0-237 

•0618 

3-67 

100 

•00142 

0-179 

0-122 

0-217 

•0556 

3-90 

110 

•00137 

0-172 

0-117 

0-208 

•0505 

412 


282 















































THE DISTRIBUTING SYSTEM 

Table LXXXIY. gives the constants for currents of 15 cycles. 


Table LXXXIV. 

Resistance, Reactance and Impedance per mile of Bull Headed Steel Rails. Standard 

Section, 15 cycles per second. 


Weight of Rail 
lbs. per yard. 

Inductance. 

Reactance. 

Virtual 

Resistance 

(ohms). 

Impedance. 

Resistance 
to D. C. 
(ohms). 

Ratio of Drop 
AC/CC. 

60 

•00182 

0-171 

0 129 

•214 

•0925 

2-31 

70 

•00173 

0-163 

0-123 

•204 

•0792 

2-57 

80 

•00165 

0156 

0-117 

•195 

•069 

2-83 

90 

•00158 

0-149 

0-112 

•186 

•0618 

3-0 

100 

•00151 

0-143 

0-107 

•179 

•0556 

3-22 

110 

•00145 

0437 

0-103 

•172 

•0505 

3-4 


Impedance of Overhead Circuit with Rail Return. 

The inductance of a circuit consisting of a copper conductor placed overhead with 
a return conductor on the ground, is a considerable factor and one which must be taken 
into account where alternating currents are used. Having already submitted Tables 
of inductance for a single rail of a standard form of section of different sizes, we have 
now to calculate the inductance of a pair of rails placed 4 ft. 8J ins. apart with an 
overhead conductor placed at a particular height. The impedance of the circuit so 
formed comprises the resistance and reactance of the overhead conductor, the 
resistance of the rails, the inductance within the rails, the inductance of the circuit 
bounded by the rails and overhead conductor and the mutual induction of the currents 
in the two rails. Owing to the impedance of the rail circuit, the track rails are not 
used to a great extent except in conjunction with boosters and copper conductors. As 
however, part of the circuit in such cases consists of the overhead conductor with track 
rails for a return, we submit a table of resistances, reactances, and impedances for a 
system consisting of a standard track with 60 lbs., 80 lbs., and 100 lbs. rail, also 
resistance and impedance of overhead conductor of No. 4/0 s.w.g., the values of 
reactances and impedances being given for 15, 20 and 25 cycles per second. 


Table LXXXY. 

Impedance of Rail portion of Circuit. 


Weight per yard—lbs. 
Resistance per mile— 
ohms. 

100 

■0278 

80 

•0345 

60 

•0462 

Cycles per second ... 

25 

20 

15 

25 

20 

15 

25 

20 

15 

Radians per second.. 

157 

125 

94-2 

157 

125 

94-2 

157 

125 

94-2 

Reactance ... 

•26 

•207 

•16 

•27 

•216 

•168 

•28 

•227 

•177 

Resistance ... 

•071 

•061 

•053 

•077 

•067 

•058 

•08 

•074 

•065 

Impedance ... 

•265 

•216 

•17 

•28 

•227 

•178 

•293 

•239 

•188 

Ratio alternate to 










continuous current 










drop . 

9-5 

7-8 

64 

84 

6-58 

5-17 

6-34 

5-17 

4-06 


283 









































ELECTRIC RAILWAY ENGINEERING 


Table LXXXY. gives the reactance, resistance and impedance per mile for the 
track portion of the circuit consisting of two rails with overhead conductor 20 ft. 
above rails for three weights of rails and for three different periodicities. 

This Table gives the ratio of the drop between two points in the track one mile 
apart for alternating currents in terms of the drop for continuous current under the 
conditions given. 

Under normal conditions, and for 25 cycles, which is a common frequency, the 
drop on the rails with alternating currents may be said to be roughly ten times the 
drop with continuous current. In consequence, the u-se of the rails for this purpose 
is very limited, and in practice the rails are supplemented by copper conductors, to 
which the rails are connected at frequent intervals. The rails and copper conductors 
form a return circuit in contact with earth, and therefore subject to the Board of 
Trade regulations affecting earthed conductors already quoted. In order to keep the 
drop within the limits prescribed, and in order to limit the amount of copper used, it 
is necessary to provide arrangements for limiting the drop in the rails. This object 
may be obtained by means of track boosters. One arrangement is that used by the 
Oerliken Company, in which the track current is transferred by boosters to a common 
return conductor. Another arrangement is that described by Carter, in his paper 


Trolley v/>rc. 



Fig. 251. Arrangement of Track Boosters for Alternating Currents. 


read before the Institution of Electrical Engineers, 25th January, 1906, in which the 
track boosters are inserted at intervals along the track, the function being to induce 
an electro-motive force opposing the track drop. These boosters are transformers of 
ratio unity, of which the primary is connected across a section insulated in the trolley 
wire, and the secondary across an insulated joint in the track, shown diagrammatically 
in Fig. 251. The transformers are secured on poles or gantry posts, and are provided 
with switches for cutting out the transformer when desired. 

We next deal with the resistance, reactance, and impedance due to currents 
in the overhead conductor, assuming that practically all the current is carried by the 
copper conductor. 

Table LXXXVI. gives the values for a mile of circuit for three different 
periodicities. 

Table LXXXYI. 


Impedance of Overhead Conductor. 


Cycles per 
Second. 

Radians per 
Second. 

Reactance. 

Resistance. 

Impedance. 

Ratio Alternate to 
Continuous-Current 
Drop. 

25 

157 

0-37 

0-342 

0-504 

1-47 

20 

125 

0-295 

0-342 

0-452 

1-32 

15 

94-2 

0-223 

0-342 

0-408 

1-19 


284 

















































THE DISTRIBUTING SYSTEM 


Table LXXXYII. gives the total impedance per mile of circuit for three 
periodicities and three weights of rail. 


Table LXXXYII. 


Total Impedance pc?’ Mile of Circuit. 


Wt. of Rail. 

25 cycles. 

20 cycles. 

15 cycles. 

lbs. per yd. 

Reactance. 

Resistance. 

Impedance. 

Reactance. 

Resistance. I Impedance. 

Reactance. 

Resistance. 

Impedance. 

100 

0-65 

0-422 

0-775 

0-522 

0-417 0-668 

0-40 

0-407 

0-571 

80 

0-64 

0-419 

0-765 

0-511 

0-41 0-655 

0-39 

0-400 

0-558 

60 

0-63 

0-413 

0-753 

0-502 

0-404 i 0-644 

0-38 

0-395 

0-548 


It will be seen on referring to the above Table, that the difference in the impedance 
values for the different conditions, are much reduced. This is owing to the effect of 
the resistance of the overhead conductor. The effect of the impedance of the rail and 
overhead conductor upon the power factor, depends upon the voltage of transmission, 
and also upon the power factor of the train circuit. 

With 500 kilowatts transmitted, and with 5,000 volts in the line, the drop in 
voltage is 18 per cent. If the voltage be 8,000 volts, and the same power transmitted, 
the drop is 30 per cent, over the mile length. These results enable the distance 
between feeding points to be determined when the voltage on the circuit is selected. 


Leakage from Track Rails. 

Where track rails are used as conductors and form part of the return circuit, 
regard must be had to the amount of current which passes from the rails to the earth. 
These currents, if not kept within limits, may injuriously affect electric cables, water 
pipes, gas pipes, and telephone lines. The injury is caused mainly by electrolytic 
action, and of the metals employed for the purposes mentioned, lead is the most 
susceptible to injury, its electro-chemical equivalent being much higher than copper 
or iron. The Board of Trade have issued regulations affecting the working of electric 
tramways and tube railways, but no regulations are in force affecting the working of 
main line railways, and such regulations as are in force do not apply to alternating 
currents. There is no doubt, however, but that the limits as to the permissible 
amount of stray currents, must be observed by railways in their own interest. Owing, 
however, to the difference between the construction of railways and tramways, the 
leakage surface is less, and it will be possible to transmit greater distances for the 
same amount of leakage. If we assume a certain length of track, and that a current 
is put in at one end and taken out at the other, it will be found that the current 
actually in the rail will diminish towards the middle of the portion of line under 
consideration. The current will leave the rail over the half section remote from the 
source, and will return to the rail over the half section nearest the source. The 
distribution of current density and potential along the rail under tramway conditions, 
was thoroughly investigated by Mr. Evan Parry. 1 The potential and current at any 

1 “ Fall of Potential along Tramway Rails,” E. Parry, Electrician, August 10th, 1900. 

285 































ELECTRIC RAILWAY ENGINEERING 


point of the rails is expressed as an exponential function of the distance from the source 
and the point chosen, and of the ratio of the cross sectional resistance of the rail to 
the contact resistance. Inasmuch as the resistance of rails to alternating current is 
greater than their resistance to continuous currents, the values of the current and 
potential along the line differ greatly. The specific values for steel of different 
compositions have already been tabulated, and also the resistance to alternating 
currents of three different periodicities. The first function referred to, or the contact 
resistance between the rail and earth is not so definitely ascertainable ; the leakage 
surface consists in the main of the chair supporting the rail. The current being 
dissipated to earth by means of the wooden sleeper, the amount of leakage will 
depend, to some extent, upon the state of the weather. From measurements made on 
a length of track, we conclude that the surface resistance may be taken at 1,500,000 
ohms per sq. in. under average conditions. Table LXXXYIII. shows the current 
entering the rail and the corresponding current density for different lengths of track with 


Table LXXXYIII. 

Table of Current Values in Track Bails for 10 Volts Difference of Potential between 

ends of Bail for 100 lb. Bail. 


Dis¬ 

tance 

in 

Miles. 

c.c. 

25 cycles. 

20 cycles. 

15 cycles. 

Density 

per 

square 

inch. 

Total 

Current. 

Per¬ 

centage 

Leakage. 

Density 

per 

square 

inch. 

Total 

Current. 

Per¬ 

centage 

Leakage. 

Density 

per 

square 

inch. 

Total 

Current. 

Per¬ 

centage 

Leakage. 

Density 

per 

square 

inch. 

Total 

Current. 

Per¬ 

centage 

Leakage. 

1 

21-4 

207 

0-5 

1-74 

16-85 

1 

2-62 

21-9 

1-8 

4-22 

40"5 

0-8 

2 

10-7 

104 

0-8 

0-897 

8-7 

4-8 

1-33 

12-7 

3-8 

2-14 

21-4 

2-0 

8 

72 

70 

1-2 

0-62 

6-0 

10-5 

0-91 

8-73 

7-0 

1-44 

13-8 

4-2 

4 

5-42 

52*5 

1-5 

0-49 

4*75 

17-3 

0-7 

6-72 

11-5 

1-11 

10-6 

7-3 

5 

483 

41-8 

2-0 

0 415 

4-02 

22-8 

0-58 

5"56 

17-5 

0-914 

8-76 

11-7 

6 

366 

35-4 

25 

0-371 

3-6 

31-9 

0-517 

4-97 

24-5 

0-79 

7-58 

17-0 

7 

3-12 

30 

3-8 

034 

3-3 

41-2 

0-47 

4*5 

330 

0-7 

6-72 

23-0 

8 

272 

263 

5*5 

0-322 

3-12 

48-0 

0-43 

412 

41-0 

064 

6-14 

28-8 

9 

246 

23-9 

8-0 

0-307 

2-97 

54-4 

0-41 

3-93 

47-0 

0-59 

5-66 

32-8 

10 

23 

22*2 

io-o 

03 

2-89 

61-0 

0-39 

3-7 

50-0 

0-56 

5 - 37 

35-8 


10 volts difference of potential between the two ends. The values are given for a 100 lb. 
rail and for continuous currents as well as for alternating currents of 15, 20 and 
25 cycles. For continuous currents, the values of current density will apply to all sizes 
of rails, but they differ for alternating currents owing to the variation of virtual resistance 
with the area of rail. The Table also shows the percentage of leakage from the rail. It 
should be noted that the percentage of leakage is much greater in the case of 
alternating currents. The limitations in the transmission of alternating currents are 
clearly brought out in the Table ; referring, for instance, to the case of transmission 
over four miles, the amount of continuous current which may be transmitted with a 
potential difference of 10 volts is 52*5 amperes per rail, and leakage 0'8 of an ampere, 
or 1*5 per cent, of the total current transmitted ; whilst for alternating currents of 
25 cycles frequency, the current transmitted for the same potential difference is six 
amperes per rail, and the leakage practically the same as in the case of continuous 
current, and equivalent to 17‘3 per cent, of the total current. 

286 































THE DISTRIBUTING SYSTEM 

Table LXXXIX. 

Table of Pressure Differences on Track Rails with 100 Amperes in Rail —100/6. Rail. 



C.C. 

25 cycles. 

20 cycles. 

15 cycles. 

Distance in Miles. 

D P. in 

Leakage, 

D. P. in 

Leakage, 

D.P. in 

Leakage, 

D.P. in 

Leakage, 


Volts. 

Amperes. 

Volts. 

Amperes. 

Volts. 

Amperes. 

Volts. 

Amperes. 

1 

4-83 

•5 

59 

1 

40 

1-8 

25 

•8 

2 

9 62 

•8 

115 

4-8 

79 

3-8 

47 

2-0 

8 

14-2 

1-2 

166 

10-5 

115 

7-0 

72 

4-2 

4 

19 

1'5 

210 

17-3 

149 

11-5 

94 

7*3 

5 

23-8 

2 0 

249 

22-8 

180 

17-5 

114 

11-7 

6 

28-2 

2-5 

278 

31-9 

200 

24-5 

134 

17-0 

7 

33-3 

3-8 

303 

41-2 

222 

33-0 

149 

23-0 

8 

38 

5'5 

320 

48 

243 

41-0 

166 

28-8 

9 

42 

8-0 

337 

54-4 

254 

470 

177 

32-8 

10 

45 

io-o 

346 

61 

267 

50-0 

186 

35-8 


Table LXXXIX. gives the potential difference for varying distances of transmission 
in a track with 100 lbs. rail carrying 100 amperes per rail. Take the case of a four-mile 
transmission; continuous current could be transmitted with a potential difference of 
19 volts and a leakage of 1*5 amperes, whereas to transmit alternating currents of *25 
cycles periodicity the same distance requires a potential difference of 210 volts, and the 
leakage would be 17 amperes. 

In the case of tube railways care should be taken to provide against contact between 
rails forming part of a return system and the lining of the tunnel, except only at or 
near the source of supply to the distributing circuit. The tube lining has an enormous 
dissipating surface compared with its cross sectional area, in consequence of which the 
leakage of current is promoted to an abnormal extent, even although the sections of 
the tunnel lining are well bonded. 


287 


























































Chapter IX 

LOCOMOTIVES AND MOTOR CARRIAGES AND THEIR ELECTRICAL 

EQUIPMENT 

/~\NE of the most important questions arising in connection with the electrification 
i ail ways relates to whether electric locomotives, or motor cars, shall be 
employed. Electric locomotives will, of course, invariably he used for freight 
haulage, so far as this work comes to be done electrically, but for passenger trains,, 
electiic locomotives do not possess an exclusive claim for consideration for all 



lig. 252. Electric Locomoti\e for New \ork Central Railroad. Weight, 85 Metric Tons. 


classes of traffic. The alternative consists in trains made up partly or entirely of 
motor cars, operated on the multiple unit control principle. 

For long distance passenger trains, there are sound advantages in the use of trains 
hauled by electric locomotives as compared with motor car trains, though for urban 
and suburban traffic these advantages will frequently be exceeded by the advantages of 
motor cai tiains. In the transition stage from steam to electric operation, it will 
involve less disarrangement of the traffic conditions to employ electric locomotives to 
a certain extent. As an instance may be mentioned the case of the New York Central 
and Hudson River Railroad Co., which has now embarked upon the most extensive 
scheme of heavy electric traction which has yet been undertaken. The tracks of this 
railway enter New lork through an extensive system of tunnels, and it has long been 
recognised that it would be of great advantage on the score not only of cleanliness and 
hygiene, but of safety, to replace steam by electricity. This has led the New York 

291 u 2 














































































































ELECTRIC RAILWAY ENGINEERING 


Central Railway to undertake the replacement of its steam suburban service by an 
electric service, and the multiple unit system, with the motors under the carriages, 
has been adopted for all suburban trains. The railway is now electrically equipping 
its New York terminal for a distance of 34 miles on the main line from the Grand 
Central Station to Croton, and for 24 miles on the Harlem division, as far as White 
Plains. All passenger traffic within this district or zone will be handled electrically, and 
the electric locomotive recently designed and built by the General Electric Co. and 
the American Locomotive Co. is the first of thirty-five for which orders have 
already been placed, and which will be used in the hauling of through passenger 
trains. According to the specified conditions, the service demanded of this type of 
locomotive is as follows. It is capable of regularly making the trip from the 



Fig. 253. Electric Locomotive for New York Central Railroad. Weight, 85 Metric Tons. 


Grand Central Station to Croton, a distance of 34 miles, hauling a total train 
weight of 400 metric tons, in 44 minutes without a stop. This corresponds 
to a speed of 46 miles per hour. The heaviest of these trains weighs 800 metric 
tons, and is drawn by two of these locomotives. The locomotive is able to haul 
a 400-ton train at a maximum speed of 70 miles per hour. Two locomotives, 
equipped with the multiple unit control system, are used to haul an 800-ton train 
at a maximum speed of 70 miles per hour. 


General Arrangement and Dimensions of the New York Central Locomotives. 

The designers have sought to secure in this locomotive the best mechanical 
features of the high speed steam locomotive, combined with the greatly increased 
power and the simplicity in control made possible by the use of electricity. 

The locomotive is illustrated in Figs. 252 and 253. It has four driving axles, on 

292 


















LOCOMOTIVES AND MOTOR CARRIAGES 

each of which is mounted the armature of a gearless electric motor having a normal 
rating of 550 h.-p. The total rated capacity of the locomotive is 2,200 h.-p. when 
estimated in accordance with the customary 1-hour basis of nominal rating of 
lailway motors. For short periods, however, a considerably greater power may be 

developed, giving the locomotive greater capacity than the largest steam locomotive in 
existence. 

The principal dimensions of the locomotive, and other data regarding it, are given 
in Table XC. 1 6 


Table XC. 

Leading Data of New York Central Elect 

Number of driving wheels 
Number of truck wheels 
Weight .... 

Weight on drivers . 

Wheel base, driving 
,, ,, total . . 

Maximum tractive force 
Ditto per metric ton engine weight 
Wheels, driving 

,, engine truck . 

Length over buffer platforms 
Extreme width 
Height to top of cab 
Diameter of driving axles 
Normal rated power 
Maximum power . 

Speed with 450-ton train 
Voltage of current supply 
Normal full load current 
Maximum full load current 
Number of motors 
Type of motor 
Rating of each motor 

Weight of motor—excluding yokes which are 
frame—but including axle 
Ditto, excluding axle 


built into 


ic Locomotive. 


the 


ocon 


otive 


8 

4 

85 metric tons 
68 metric tons 

13 ft. 

27 ft. 

34,000 lbs. 

400 lbs. 

44 ins. dia. 

36 ins. dia. 

37 ft. 

10 ft. 

14 ft. 10 ins. 
8 - 5 inches. 

2.200 h.-p. 
3,000 h.-p. 

60 m.p.h. 

600 

3,050 amps. 
4,300 amps. 

4 

GE-84-A 
550 h.-p. 

11.200 lbs. 
9,430 lbs. 


The weight of the electrical equipment per locomotive is made up as set forth in 
Table XCI. 

Table XCI. 

Weight of Electrical Equipment of New York Central Locomotive. 

Total weight of four motors (excluding axles and also excluding yokes 


which are part of the locomotive frame, but including armature, 


field coils, and laminated poles) ....... 

37,700 lbs. 

Weight of twenty rheostats ......... 

4,600 „ 

Weight of two master controllers ....... 

Weight of control equipment, including rheostats and master 

600 ,, 

controllers ............ 

10,200 „ 

Weight of air compressor ......... 

4,300 „ 

Cables, cleats, etc. .......... 

3,000 ,, 

Total weight of electrical equipment ....... 

55,200 lbs., or 25 
metric tons. 


1 This descriptive matter is partly compiled from bulletins published by the General Electric Co. 
of America, the contractors for equipping the road. 

293 












ELECTRIC RAILWAY ENGINEERING 

The weight of the magnetic } T oke which was furnished as part of the locomotrv e, 
and is not included in the above figures, as it also forms part of the mechanical frame 
of the locomotive, is 11,900 lbs., or 5'4 metric tons. 

It would seem reasonable to add half of this to the weight of the electiical equip¬ 
ment, which is thus brought up to 27'7 metric tons, or 326 per cent, of the total 
weight of the locomotive. 

The largest of the present New York Central types of steam locomotives, i.e., 
the “ 999 ” type, have a capacity of only 1,500 h.-p. per locomotive. 

The Electric Motors for the New York Central Locomotives. 

The motors mark an interesting and radical departure from ordinary motor 
construction. 'The designers have arranged the armatures directly upon the axles, 



Fig. 254. Assembly of Truck of New York Central Locomotive. 

partly with a view to securing the advantage of direct application of power to the 

driving axles and to avoiding the losses of power in gear and pinion which are 

encountered in geared railway motors. 

There are only two pole pieces, which are practically part of the truck frame, and 
have nearly fiat vertical faces. There is no necessity, therefore, of preserving a rigid 
alignment between armature and field, and the armature can have a large free vertical 

movement without danger of striking the pole pieces. The maximum weight of the 

motor, consisting of its field and frame, is carried with the truck frame upon the 
journal box springs on the outside of the driving wheels. 

This construction, besides being strong and simple in design, greatly facilitates 
repairs and renewals, as an armature, together with its wheels and axles, may be 

294 































LOCOMOTIVES AND MOTOR CARRIAGES 


removed by lowering the complete element without disturbing the fields or any other 
part of the locomotive, and a new element may be inserted in its place. All parts are 
especially accessible for inspection and cleaning. 

The dead weight on each driving axle is practically the same as on an ordinary 
steam locomotive, and is about 10 per cent, less than that on the heaviest types, while, 
in addition, there is no unbalanced weight to produce vibration, with attendant injuries 
to track and road bed construction. It is anticipated that this will effect such a reduc¬ 
tion in the expense of maintaining the rails and road bed, due to the absence of pounding 
and rolling, as to have an important bearing on the upkeep of the permanent way. 

A longitudinal section of the locomotive frame may be seen in Fig. 252. The main 
frame is of cast steel, and forms not only the mechanical frame of the locomotive, but 
also part of the magnetic circuit of the motors. It will be seen that the magnet 
fields are arranged in tandem, the end pole pieces being cast as part of the end frames, 
and the double pole pieces between the armatures being carried by heavy steel transoms 
bolted to the side frame, and forming part of the magnetic circuit as well as constituting 



Fig. 255. Motor Armature of New York Central Locomotive. 


cross braces for the truck. The field coils are wound upon metal spools which are 
bolted upon the pole pieces. A suitable distribution and division of the weight of the 
locomotive among the axles has been accomplished by suspending the main frame 
and superstructure from a system of half-elliptic springs and equalised levers of forged 
steel, the whole being so arranged as to cross-equalise the load and to furnish three 
points of support. A photograph of the truck is shown in Fig. 254, while Fig. 255 
shows a motor armature. 

Control System of the New York Central Electric Locomotive. 

The method of control is the multiple unit system. The engineer handles a 
small controller, which operates the control circuit. The current in this control 
circuit operates in turn the main contactors, admitting current to the powei ciicuit, 
The master controller is located in the motorman s cab, while the contactors aie 
located in the spaces at the forward and rear ends of the locomotive. 

By use of this system, two or more locomotives can be coupled and operated from 
the leading cab as a single unit. The motive power may thus be adapted to the 

295 









ELECTRIC RAILWAY ENGINEERING 

weight of the train. A single locomotive will be able to maintain the schedule with 
a 400-ton train, and two locomotives coupled together will be used to operate heavier 
trains, with a single engine crew operating both locomotives simultaneously. 

The control system permits three running connections; namely, four motors in 
series, two groups of tw T o in series-parallel, all four motors in parallel. The motor- 
reverser, contactors, rheostats, and other controlling appliances are all of the Sprague 
General Electric multiple unit type. The master controller is fitted with a special 
operating lever about 24 ins. long, and capable of being moved through an angle of 
about 75 degrees. A current-limiting device is provided in the master controller, and 
consists of a friction clutch operated by an electric magnet which is energised by the 
current passing through one of the motors, the arrangement being such that when 



Fig, 256. Sectional View of Air Compressor for New York 

Central Locomotive. 


the current exceeds a predetermined amount the cylinder cannot be rotated further 
until the current has fallen sufficiently to allow the relay to drop. As long as the 
current does not exceed the desired limit the automatic feature is not in operation. 


Auxiliary Apparatus for the New York Central Locomotive. 

The superstructure consists of a central cab for the operator, containing master 
controllers, engineer’s valves for air brake, and switches and valves required for 
operating the sanding, whistling, and bell-ringing devices. This apparatus is furnished 
in duplicate, one set on each side of the cab, and is arranged so as to be easily 
manipulated from the operator’s seat, while at the same time a practically unobstructed 
view to front and rear may be obtained from the windows. The air gauge, meters, 
etc., are located so as to be easily read by the driver. 

There is a central corridor extending through the cab so as to permit access from 

296 


























































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 


the locomotive to the cars behind, and the contactors, rheostats, and reversers are 
arranged along the sides of these corridors in boxes of sheet steel, which are sheathed 
on the inside with fireproof insulating material. All of these appliances are, therefore, 
easily accessible for repairs or inspection. 

In the operator’s cab there is placed a motor-driven direct-connected air compressor, 
running at 175 revolutions per minute, and having a capacity of 75 cubic ft. of free 



air per minute. The compressor is controlled by a governor which automatically 
cuts the motors in and out of circuit when the air pressure falls below 125 lbs. or 
exceeds 135 lbs. 


Contact Collecting Devices for the Neiv York 
Central Locomotive. 



A sectional view of the compressor is shown in Fig. 256. To economise space 
and simplify the bearings, the compressor is provided with two motors, which are 
connected in series with each other. The 
compressed air is employed both for braking 
the train and blowing the whistle. 


Current is collected from the third rail 
by multiple-contact spring-actuated third-rail 
shoes, the supports of which are carried on 
channel irons attached to the journal box. A 
photograph of the third-rail shoe is given in 
Fig. 257. There are four of these shoes on 
each side of the locomotive. In the yards at 
the terminal, the large number of switches 
and crossings necessitates an overhead con¬ 
struction in places, and additional contact 
shoes, one of which is shown in Fig. 258, 
are, therefore, mounted on the top of the Fig. 258. Overhead Contact Device of 
locomotive for collecting current when the New York Central Locomotive. 
locomotive is passing over these points. This 

device may be raised and lowered by air pressure controlled from the engineer’s cab. 
A magnetic ribbon fuse is placed in circuit with each shoe and overhead contact 
device, so as to secure protection in case of accidental short circuit. 

297 





ELECTRIC RAILWAY ENGINEERING 

New York Central Locomotive Tests. 

In Fig. 259 are given the tractive force and speed curves for one of these 
locomotives when all four motors are connected in parallel, as published in 1904 by 
the General Electric Co., and presumably based on factory tests of the motors. 

The New York Central and Hudson River Railroad Co. and the General Electric Co. 
are making extensive preliminary tests and trials of these locomotives under all 
conditions likely to obtain in service operation. For this purpose, the New York Central 





Amperes per Locomotive 

Fig. 259. Characteristic Curves of New York Central Locomotive. 


and Hudson River Railroad Co. has set aside a 6-mile stretch of track on its main line 
between Schenectady and Hoffman’s Ferry, and has equipped it with standard third- 
rail construction. The track is well ballasted and practically straight, and permits of 
attaining a maximum speed of from 70 to 80 miles per hour. 

Power for operating the locomotive is furnished by the General Electric Co., of 
Schenectady, U.S.A., and for this purpose there has been installed in the new power¬ 
house at the Schenectady Works a 2,000-kilowatt three-phase 25-cycle Curtis 
turbine-generator delivering energy to the line at a pressure of 11,000 volts. 

298 


























































LOCOMOTIVES AND MOTOR CARRIAGES 


W 

M 

O 


A special high tension 
transmission line has been 
constructed from the power- 
station for a distance of 
5 miles to the sub-station 
at Wyatt’s Crossing. 

The sub-station contains 
a 1,500-kilowatt, 650-volt 
rotary converter with static 
transformers for reducing 
the pressure from 11,000 
volts to 475 volts alterna¬ 
ting current at the collector 
rings, and then to 600 volts 
continuous current for the 
locomotive. 

The location and ar¬ 
rangement of the apparatus 
in the sub-station and the 
dimensions of the station 
are in general the same as 
for the sub-stations within 
the electric zone at the New 
York City terminus. The 
installation thus afforded 
practical experience with the 
system in detail in advance 
of construction, and while 
the locomotive tests were 
being made. 

A complete set of re¬ 
cording instruments has 
been installed in the cab 
for the purpose of making 
these tests. These instru¬ 
ments, when in operation, 
indicate automatically and 
continuously the speed and 
power developed by the 
locomotive. 


New York Central Locomotive 
Tests of November, 1904. 

Two sets of curves are 
given in Figs. 260 and 261 
showing the current input, 
voltage, and speed at the 
locomotive when starting, 




299 


Fig. 260. Curves of Current Input, Voltage and Speed of New York Fig. 261. Curves of Current Input, A'oltage and Speed of New 
Central Locomotive with Eight-Car Train. Central Locomotive with Four-Car Train. 




















































































































































ELECTRIC RAILWAY ENGINEERING 


and running with an eight-car train weighing 300 metric tons and a four-car train 
weighing 155 metric tons, both exclusive of locomotive. The total weight of the train, 
including locomotive and passengers, was 390 metric tons and 240 metric tons for the 
eight-car and four-car trains respectively. The maximum speed reached w 7 as 03 miles 
per hour with an eight-car train, and 72 miles per hour with a four-car train. 

It will be noted that the trains were still accelerating at these speeds, but the 
length of the track which had at that time been equipped did not permit of attaining 
higher speeds. 

The New York Central locomotives were not designed for abnormally high 
speeds at intervals, but rather with a view to obtaining a high average schedule, due 



Fig. 262. New York. Central Locomotive Hauling a Six-car Train during one of the 

Tests of November, 1904. 


to their ability to accelerate more rapidly than is possible with the present steam 
locomotive. 

In starting tests, with an eight-car train weighing with the locomotive 390 metric 
tons, a speed of 30 miles per hour has been reached in 60 seconds, corresponding to an 
acceleration of half a mile per hour per second. During certain periods of the 
acceleration the increase in speed amounted to 0'6 mile per hour per second, requiring 
a tractive effort of approximately 27,000 lbs. developed at the rim of the locomotive 
drivers. Ibis value was somewhat exceeded with the four-car train, where a momentary 
input of 4,200 amperes developed a tractive effort of 31,000 lbs. at the drivers, with a 
coefficient of traction of 22'5 per cent, of the weight on drivers. The average rate of 
acceleration with the four-car train, weighing, including the locomotive, 240 metric 
tons, was 30 miles in 37J seconds, or 0‘8 mile per hour per second, calling for an 
average tractive effort of 22,000 lbs. 


300 









LOCOMOTIVES AND MOTOR CARRIAGES 


The maximum input recorded, 4,200 amperes at 460 volts, or 1,935 kilowatts, 
gives a motor output of 2,200 h.-p. available at the wheel. With 4,200 amperes and 
a maintained potential of 600 volts there would have been an input to the locomotive 
of 2,520 kilowatts, corresponding to 2,870 h.-p. output from the motors. As this output 
is stated to be secured without exceeding the safe commutation limits of the motors, 
and with a tractive coefficient of 22*5 per cent, of the weight upon the drivers, the 
electric locomotive is placed well in advance of the steam locomotive. 

Throughout both the starting and running tests the electric locomotive has shown 
remarkable steadiness in running, a distinct contrast in this respect to the steam 
locomotive, especially should the latter be forced to perform the work accomplished by 
the electric locomotive. 

Fig. 262 is a photograph of the first locomotive when hauling a six-car train. 


New York Central Locomotive Tests of April, 1905. 

Further tests were made on April 29th, 1905, over the experimental track at 
Schenectady, N.Y., for the purpose of securing data on the relative acceleration and 



Fig. 263.— Profile of Alignment and Grades of New York 
Central Experimental Track. 


speed characteristics of electric and steam locomotives. The tests were made with the 
New York Central type electric locomotive 6,000, already described, and on the Pacific 
type steam passenger locomotive 2,797. The data secured were intended for private 
information, but the results achieved were considered to be so remarkable that the 
parties concerned decided to make public a resume of the runs. 


Time of Test and Weather Conditions. 

The test started about 8 a.m., and continued until about 1 p.m.,of April 29th, 1905, 
temperature averaging about 50 degrees F. During the time of the test no rain fell, 
so that the rails were perfectly dry. 


301 




























ELECTRIC RAILWAY ENGINEERING 


QffiCpQ c 0 

-7-0—*J* — 13-0- -+-7-0-—4*<-77 

H-----WJ-llX--J 


1 § § 
|S l» I!? |4 

' Weight 00 Drivers 
[• -llC.OUO lbs.- 

-Total Weight 200,500 lbs.- 


Description of Experimental Track. 

The experimental track, 6 miles in length, was the portion of old track No. 4 
of the New York Central main line, formerly used for east-bound freight movements 
between mile-posts 162 and 168, west of Schenectady. 

The track materials were 80-lb. standard New York Central section steel rail, with 
six-bolt 86-in. splices, sixteen yellow pine ties to the 30-ft. rail, gravel ballast, well 

surfaced, curves elevated for 
a speed of about 70 miles per 
hour. 

The working conductor 
consisted of top-contact 1 70-lb. 
steel rail reinforced with copper 
and covered in part with a 
board protection. At four 
crossings, overhead construc¬ 
tion was used to cover gaps 
where the use of the third rail 
was inadmissible. 

The alignment and grades 
are illustrated upon the con¬ 
densed profile of Fig. 263. It 
will be noted that from the 
easterly end of the track at 
mile-post 162, going westerly, 
the rising gradients varied 
from 5 ft. to 17 ft. per mile to 
a summit between mile-posts 
166 and 167, and thence the 
track descended on gradients varying from 6 ft. to 19 ft. per mile to the end of the 
track at mile-post 168. It will also be noted that in the 6 miles there were seven 
curves, varying from 0 degrees 48 minutes to 2 degrees 17 minutes, the maximum 
length of tangent being 7,565 ft. 


ip" u (1) 


OQ 




-O 


S 











•s 

|o 


IS 


is 


I” |« 

1 • Total Weieht Tender 

P-loaded 127,000 lbs.— 


h 


-67-7^- 


U Wt. on Driven ^ 

141.000 lb» —>1 

-Total Weight.Locomotive Only, 215,000 lbs 


-Gnuid Total,Locomotive Complete 312,000 lbs.- 


Street Ry. Journal 


Fig. 


264. Diagram of Governing Dimensions and 
Weights of New York Central Steam and Electric 
Locomotives employed in Tests made April 29th 1905. 


Source of Power, Transmission Line, and Sub-station. 

These were the same as for the tests of November, 1904. The sub-station was near 
mile-post 165. 


Dimensions and, Weights of the Test Trains. 

The diagram of Fig. 264 illustrates the governing dimensions and weights of both 
locomotives. The weights of the cars are given in Table XCII. 


1 Experiments have also been made with an alternative type of under-contact rail which has a 
number of advantages over the ordinary top-contact third rail. 


302 























































LOCOMOTIVES AND MOTOR CARRIAGES 

Table XCIL 

Composition of Trains in New York Central Tests of April, 1905. 



Electric Train. 


Steam Train. 

Car No. 

Weight loaded, 
lbs. 

Car No. 

Weight, lbs. 

(No Load.) 

Eight-car train — 






1 . 

1,060 

101,900 

1 

2,527 

79,900 

2 . 

1,070 

100,400 

2 ... . 

1,547 

86,100 

3 . 

1,082 

106,200 

3 

1,534 

87,800 

4 . 

1,092 

100,100 

4 

1,521 

84,500 

5 ... . 

1,097 

104,650 

5 

1,069 

86,300 

6 ... . 

1,550 

102,800 

6 . 

1,099 

87,400 

7 ... . 

1,552 

106,000 

7 ... . 

1,563 

86,400 

8 ... . 

1,558 

104,750 

8 ... . 

1,513 

86,700 

Locomotive . 

— 

200,500 

Locomotive 

— 

342,000 

Total . 

— 

465’5 tons. 

Total . 

— 

465 tons. 

Six-car train — 






1 . 

1,060 

101,900 

1 . 

2,527 

79,900 

2 ... . 

1,070 

100,400 

2 ... . 

1,547 

86,100 

3 ... . 

1,092 

100,100 

3 ... . 

1,534 

87,800 

4 ... . 

1,097 

104,650 

4 ... . 

1,521 

84,500 

5 ... . 

1,550 

102,800 

5 ... . 

1,069 

86,300 

6 ... . 

1,558 

104,750 

6 ... . 

1,099 

87,400 

Locomotive . 

— 

200,500 

Locomotive 

— 

342,000 

Total . 

— 

370 tons. 

Total . 

— 

388 tons. 


In Table XCIII., which gives the average voltage at the live rail during accelera¬ 
tion, it will be noted that, due to the restricted cross-section of conductors, the voltage 
during acceleration dropped considerably more than is the case in actual practice 
within the electric zone in the neighbourhood of New York. Therefore the results 
obtained in this comparative test are much less favourable for the electric locomotive 
than are secured in actual practice. 


Table XCIII. 


Average Voltage at Live Hail during Acceleration. 


Buns. 

Series. 

Series Multiple. 

Multiple. 

A 

520 

540 

235 

B 

620 

520 

275 

C 

600 

540 

330 

D 

680 

680 

515 

E 

650 

600 

420 

F 

600 

620 

455 


Schedule of Runs. 

Run “A.”—The “ Pacific” type steam locomotive had an eight-car train with a 
total weight, including the locomotive, of 465‘0 tons, as compared with the eight-car 
train including the electric locomotive weighing 465'5 tons. Both tiains staited togethei, 

303 


























































ELECTRIC RAILWAY ENGINEERING 


with the steam locomotive accelerating faster than the electric locomotive, clue to the 
abnormal drop in voltage from the pressure at the station of 700 volts to a track 
voltage as low as 235 volts. At 3,000 ft. from the starting-point, the electric locomotive 
gained the same speed as the steam locomotive, and from that point accelerated more 
rapidly, so that at a distance of 2 miles from the starting-point the electric locomo¬ 
tive passed the steam locomotive, and, at the shutting-off point, was two train lengths 
ahead. 

Maximum speed of steam locomotive, 50 m.p.h. 

Maximum speed of electric locomotive, 57 m.p.h. 

Run “ B.”—This run was made under the same conditions as run “ A,” with 
results practically the same, except that the speeds were higher, as follows:— 

Maximum speed of steam locomotive, 53'6 m.p.h. 

Maximum speed of electric locomotive, 60 m.p.h. 

Run “ C.”—This run was made with six-car trains for both locomotives, with total 
train weights as follows :— 

Electric locomotive . . . . . 370 tons. 

Steam locomotive ...... 388 ,, 

Owing to the extremely low voltage under the conditions above stated, which 
during acceleration fell as low as 330 volts, the steam locomotive at first accelerated 
more rapidly, but at the end of about a mile, the electric locomotive overtook the steam 
train and continued to forge ahead until the power was shut off. 

Maximum speed of electric locomotive, 61 - 6 m.p.h. 

Maximum speed of steam locomotive, 58 m.p.h. 

Run “D.”—In order to secure results as nearly as possible comparable with 
the conditions of voltage that will obtain in the actual operating zone, this run 
with six-car trains, similar to those used in run “ C,” was started at a point nearer the 
sub-station, near mile-post 164. For this run the electric locomotive, from the first 
turn of the wheels, accelerated more rapidly than the steam locomotive; and at a 
distance of 1,500 ft. from the starting-point, the electric locomotive led by a train length. 
The diagram in Fig. 265 shows the acceleration and speed-time curves for this run. 

Run “E.”—This run was made with the electric locomotive and one coach, and 
a maximum speed of 79 miles per hour was attained. 

Run “F.”—This run was made with the electric locomotive running light and 
with the power shut off on curves. A maximum speed of 80'2 miles per hour was 
attained. Had it not been necessary to shut off the current on curves, it is believed 
that the locomotive would have attained a speed of over 90 miles per hour in this 
comparatively short run. (A speed test on May 1st reached 85 miles per hour, with 
a limitation on the 2-degree 17-minute curve of 78 miles per hour.) 


Riding Qualities. 

At all speeds the smooth riding qualities of the electric locomotive were very 
noticeable, especially the lack of “ nosing ” effects. After the runs the track was 
carefully examined, and no tendency to spread rails was discovered. However, on the 
sharper curves the high speeds caused the track to shift bodily in the ballast, due to 
insufficient superelevation of the outer rail. 

304 


LOCOMOTIVES AND MOTOR CARRIAGES 

Summary. 

The most important test is run “ D,” as the voltage during that test more nearly 
approached the conditions that will be obtained in the electric zone. Therefore the 
comparison of steam and electric locomotives, given in Table XCIV., and based upon 
the results of run “D,” are very interesting as illustrating the marked superiority in 



Fig. 265. Acceleration and Speed-time Curves for Run D 
of New York Central Locomotive Tests. 


acceleration of the electric locomotive over the steam locomotive. This is clearly the 
case, since the “ Pacific” type of steam locomotive has practically the same weight 
upon the drivers. 


Table XCIV. 

Comparison of Steam and Electric Locomotives on New York Central Railway. 



Steam. 

Electric. 

Difference in favour 
of Electric. 

Length over all. 

Total weight (including tender for steam 

67 ft. 7f ins. 

36 ft. llj ins. 

30 ft. ins. 

locomotive) ..... 

342,000 lbs. 

200,500 lbs. 

141,500 lbs. 

Concentrated weight on each driving axle . 

47,000 „ 

35,500 „ 

11,500 ,, 

Revenue-bearing load back of locomotive 
Acceleration m.p.h.p.s. averaging up to 

232 tons. 

279 tons. 

47 tons. 

50 m.p.h.. 

0-246 

0-394 

0-148 

Time required to reach speed of 50 m.p.h. . 

203 seconds. 

127 seconds. 

76 seconds. 


New York Central Locomotive Tests of September 7th, 1905. 

These tests were carried out with the electric locomotive hauling a train of eleven 
cars, the first of which was a dynamometer car. The curves in Fig. 266 show the 
E.R.E. 305 X 




















































































ELECTRIC RAILWAY ENGINEERING 



c 

o 

o 

t 1 


^HUJ 


03 rs» 'O v> v> > 


© Jp 


8 




linj^ZMVjg-aai §§§§§§§§§ 


o o 
o o ~ 
° 

<X| 



306 


th 

£ 


266. Acceleration Test on New York Central Electric Fig. 267. Speed Run op New York Central Electric Locomotive 

Locomotive hauling a Train of Eleven Cars. hauling a Train of Eleven Cars. 










































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 


results obtained on an acceleration test, 
recording instruments. 


All the records were taken on automatic 


Ihe draw-bar curve was taken on the dynamometer car, with unclamped recording 
pointei. Ihe shape of this curve shows the much steadier pull of the electric loco¬ 
motive as compared to that of the steam locomotive. 

The weight behind the electric locomotive was 305 metric tons, and the weight of 
the complete train, including locomotive, was 394 metric tons. 


The results for a run over a much greater distance (44 miles), are plotted in the 
curves of Fig. 267. 


Completion of 100,000 miles Endurance Test on New York Central Locomotive, 

No. 6,000. 

In October, 1905, the first half of the 50,000 mile endurance run of the first 
high speed electric locomotive, built jointly by the General Electric Company and 
American Locomotive Company, was completed on the test tracks of the New York 
Cential lines in Schenectady. On June 12th this locomotive completed the second 
half of this exhaustive service test. The maintenance expense per mile for the 
complete 50,000 mile run amounted to less than seven-tenths of a penny. This figure 
includes all maintenance expense on motors, brake shoes, tyres, inspection, and other 
miscellaneous items. Moreover, the operating conditions were much more severe than 
those to which the thirty-five electric locomotives, which have been ordered, will be 
subjected. The test locomotive hauled a train averaging 200 to 400 tons over a six 
mile tiack, and high speed running under these conditions involved higher braking 
and accelerating duty than in regular operating service. 

According to a statement appearing in the technical press in August, 1906, eight 
of the thirty-five 100-ton 2,200 h.-p. electric locomotives which the manufacturers 
lia\e built for the New York Central Lines, follow the same design as the locomotive 
No. 6,000, which has made this satisfactory record. There are in all fourteen 
machines now complete. Of the eight locomotives noted, tv r o have been shipped to 
New York. The remaining locomotives are well under way at the shops of the General 
Electiic Company and the American Locomotive Works, and it is expected that the 
complete number, thirty-five, will be ready for service early in October, 1906. 


THE BALTIMORE AND OHIO 1896 GEARLESS LOCOMOTIVES. 

\\ hile the New York Central electric locomotives for express passenger trains are 
the most powerful in the world, largely in virtue of their high speed, they just fall short 
of being the heaviest electiic locomotives. The heaviest are the slow-speed locomotives 
employed for hauling freight and passenger trains through the Baltimore Belt Line 
Tunnel of the Baltimore and Ohio Railway. The earliest type of electric locomotive 
employed by the Baltimore and Ohio Railway is illustrated in Fig. 268 and weighs 
87 metric tons. These locomotives, three of which were placed in service in 1896, are 
each capable of hauling 2,300-ton freight trains at a speed of 10 miles per hour. ’ An 
1,800-ton train has been hauled at 12 miles per hour, and a 500-ton train at 35 miles 
per hour. The 1896 Baltimore and Ohio locomotive, like the New York Central 
locomotive, has gearless motors, but these have six poles, whereas the New York 
Central motors are bipolar. These 87-ton Baltimore and Ohio locomotives of 1896 

307 


x 2 


ELECTRIC RAILWAY ENGINEERING 


are each equipped with four General Electric type A X B 70 railway motors, each of a 
nominal rating of 180 li.-p. at 300 volts, or a total of 720 h.-p. per locomotive. Thus, 
although this Baltimore and Ohio locomotive is slightly heavier than the New’ York 
Central locomotive, it is of but one-third the horse-power capacity of the latter. The 



-fntui 












Fig. 268. Baltimore and Ohio 1896 Gearless Six-pole Locomotive. Complete weight, 87 metric tons. 

armature is spring-suspended upon a quill surrounding the axle. The field is spring- 
supported to the frame, and centred upon this quill by means of bearings. The 
principal data of the locomotive are given in Table XCY. 


Table XCV. 

Leading Data of Baltimore and Ohio 1896 Gearless Locomotive. 

Weight of locomotive, 87 metric tons. 

Number of units, 1. 

Type of motor, A X B 70 (General Electric Co. of U.S.A.). 

Nominal horse-power rating of each motor at 600 volts = 360 h.-p. 

,, ,, ,, ,, at 300 volts = 180 h.-p. 

Gearless. 

Number of trucks, 2. 

Number of motors, 4. 

Weight on driving wheels, 87 metric tons. 

Total tractive effort at full load on motors, 28,000 lbs. 

308 


































LOCOMOTIVES AND MOTOR CARRIAGES 

Table XCV. — continued. 

Total tractive effort at starting, assuming 25 per cent, tractive coefficient, 48,000 lbs. 
Gauge, 4 ft. 8J ins. 

Diameter of driving wheel, 62 ins. 

Length of locomotive over all, 85 ft. 

Extreme width, 9 ft. 5 in. 

Height to top of cab, 13 ft. Ilf ins. 

Total wheel base, about 23 ft. 

Wheel base of each truck, 6 ft. 10 ins. 

Motor axle (sleeve) bearings, 7i ins. X 13 ins. diameter. 

Journal bearings, 8£ ins. X 6 ins. diameter. 

Owing to the low speed required, the motors were permanently connected two in 
series, so that in accelerating the transition was from all four motors in series to two 



Fig. 2G8 a. Truck of Baltimore and Ohio 1896 Gearless Locomotive, showing Motor 

in Place. 


parallel pairs in series. This method of running the motors gave to the locomotive an 
aggregate nominal rating of 720 h.-p. 

As originally installed, these locomotives were designed to take power from a 
trolley at an average pressure of about 625 volts. Due to changes in the conditions 
of operation, it was later found more economical to adopt a third-rail system. 

The original tests made after these three locomotives had been put into service in 
1896 exceeded the most sanguine expectations which had been formed at that com¬ 
paratively early date. It was found that one locomotive could accelerate a loaded 
train equivalent to fifty-two freight cars having a total weight of 1,900 tons. This 
acceleration was accomplished smoothly on a grade of 0’8 of 1 per cent., and the train 
finally brought up to a speed of 12 miles per hour. The draw-bar pull exerted during 

309 














ELFXTRIC RAILWAY ENGINEERING 


acceleration was 68,000 lbs., and the current taken by the locomotive from the line at 
625 volts was 2,200 amperes during acceleration, steadying down at constant speed to 
1,800 amperes. 

Applying to this data the rule that a tractive force of 100 lbs. per ton produces 
an acceleration of 1 m.p.h. per second, and allowing for the up-grade of 0’8 of 
1 per cent., we have :— 

Total tractive force = 63.000 = 33‘2 lbs. per ton. 

1,900 

Tractive force for 0‘8 per cent, grade = 0*8 X 22 = 17*6 lbs. per ton. 

Accelerating tractive force = 33‘2 - 17 - 6 = 15'6 lbs. per ton. 

Bate of acceleration = 0*156 m.p.h. per second. 

Time required to obtain a speed of 1*2 m.p.h. = 12 =77 seconds. 

0156 

Output during acceleration = 2,200 X 625 = 1,380 k.w. 

1,000 

Energy consumed during acceleration = 1,380 X 72 = 29'5 k.w.h. 

3,600 

One of the trucks of an 1896 Baltimore and Ohio locomotive is shown in 
Fig. 268 a. 


'The Baltimore and Ohio 1903 Geared Locomotives. 

Two new two-unit locomotives weighing 146 tons per pair (or 73 tons per individual 
locomotive) have recently been supplied to the Baltimore and Ohio road. A unit of 



Fig. 269. One Component of 1903 Baltimore and Ohio Locomotive. 


one of these is illustrated in Fig. 269, while Fig. 270 shows a photograph of a 
complete two-unit set. Fig. 271 shows an interior view ; Fig. 272 is a photograph 
of the frame. 

Each individual locomotive is equipped with four 200 nominal h.-p., four-pole, 
geared, one-turn, G.E. 65 B. motors, or about 1,600 nominal h.-p. for the complete 
double locomotive with eight motors. The ratio of gearing is 81 : 19, or 4*26. 

310 


































































































































LOCOMOTIVES AND MOTOR CARRIAGES 

It was specified that this two-unit locomotive should handle a train of a weight 
of 1,450 metric tons, exclusive of the weight of the locomotive itself, on the Baltimore 
and Ohio Trunk Line through the tunnel over a 1^ per cent, grade, at a speed of 
9 miles per hour on a 625-volt circuit. 

Assuming an accelerating rate of 0'25 m.p.h. per second, a tractive force of 25 lbs. 
per ton would be required for acceleration. A further tractive force of 33 lbs. per ton 
would be required for the 1J per cent, grade. This gives a total tractive force of 
25 + 33 = 58 lbs. per ton, or 58 X 1,450 = 84,000 lbs. for the entire 1,450 tons. 
Adding the weight of the 2-unit locomotive (146 tons), gives a tractive force from the 

motors of — ^^q 146 X 84,000 = 92,000 lbs. 

Ihe controlling apparatus consists of a multiple-unit control system so arranged 
as to be able to operate each section independently, or tw T o or more sections coupled 



Fig. 270. Baltimore and Ohio Two-unit 1903 Locomotive, with Geared Four-pole Motors. 

AVeight of Two-unit Combination, 146 tons. 


together. The cab is of the box type. The master controllers, driver’s valves, etc., 
are in duplicate, a complete set being located in diagonally opposite corners of each 
cab, so that the driver can, when it best serves the purpose, operate from whichever 
end of the locomotive corresponds to the direction of motion. 

Glass doors and windows furnish an unobstructed view of the track and 
surroundings in all directions. There is also a large space under the cab floor to 
facilitate inspection of the motors and truck gear. 

The main body of the truck frame consists of a rectangular framework of cast 
steel, made up of four heavy pieces, tw 7 o side frames and two end frames. The parts 
are machined at the ends and securely fitted and bolted together, thus forming a 
strong and rigid structure capable of withstanding severe shocks without injury. The 
end pieces form the buffer beams, and to these is attached a draft gear of approved 
design which will withstand a maximum tractive force of 100,000 lbs. The draft gear 
permits of both longitudinal and lateral motion. The truck frames are supported at four 

3i i 






















ELECTRIC RAILWAY ENGINEERING 
























12 


Fig. 271. Interior of One-unit of Baltimore and Ohio 1903 Electric Locomotive, 






















LOCOMOTIVES AND MOTOR CARRIAGES 

points on equalisers. Each equaliser rests on half-elliptic springs, the ends of which 
rest on the journal boxes. In construction, the journal boxes are similar to those used 
m standard railway practice, except that they are larger and stronger. The brasses 



Fig. 272. Frame of One-unit of Baltimore and Ohio 1903 Electric Locomotive. 


may readily be removed without moving the wheels and axles or other parts of 
the truck. 

The principal dimensions of the locomotive are given in Table XCVI. 


Table 

Principal Dimensions of Baltimore and 
Weight of locomotive 

Number of units .... 
Type of motor ..... 
Horse-power rating of each motor 
Gearing ratio ..... 
Rigid frame. 

Number of motors (4 per unit) . 
Number of driving wheels (8 per unit) 

3G 


XCVI. 

Ohio 1903 Geared Two-unit Locomotive. 

146 metric tons (73 metric 
tons per unit) 

. 2 

G.E. 65 B 

200 h.-p. at 625 volts 
. 81/19 = 4-26. 

. 8 
. 16 









ELECTRIC RAILWAY ENGINEERING 


Table XCYI.— continued. 


Principal Dimensions of Baltimore and Ohio 1903 Geared Two-unit 

Lccomoti ve—co n ti nued. 


Weight on driving wheels (73 metric tons per unit) . 
Total tractive effort for two units at full load on motors 
,, ,, at starting up, assuming 25 pei 

cent, tractive coefficient . 

Gauge . 

Diameter of driving wheels .... 

Length over all (for one unit, 29 ft. 7 ins.) 

Wheel base of each unit ..... 

Extreme width (over cab roof) .... 

Width to outside of third rail shoe supports 
Height to top of cab ...... 

,, ,, of bell ...... 

Motor axle bearings ...... 

Journal bearings ...... 


146 tons 
70,000 lbs. 

80,000 lbs. 

4 ft. 8J ins. 

42 ins. 

58 ft. 7^ ins. 

14 ft. 6f ins. 

9 ft. 5^ ins. 

10 ft. 7^ ins. 

13 ft. 8 ins. 

14 ft. 9j ins. 

14 ins. X 8 ins. diameter 
12 ins. X 6 ins. diameter 


The weight of the electrical equipment per component unit, is made up as showm 
in Table XCVII. 


Table XCYII. 

Weight of Electrical Equipment of Baltimore and Ohio 1903 Geared Two-unit 

Locomotive. 


Four motors, each weighing 8,855 lbs., complete with gear and case . 35,420 lbs 

Weight of twenty-three rheostats ........ 2,760 ,, 

Weight of two master controllers ........ 496 ,, 

Weight of complete control apparatus, including master controllers 

and rheostats. 5,710 ,, 

Weight of air compressor 1,600 ,, 

Weight of cables and miscellaneous accessories ..... 2,000 


Total weight of electrical equipment 
or 20-4 metric tons, or 28 per cent, of the total weight per unit. 


44,730 lbs., 


lhe locomotive carries the customary whistle, bell, head-lights, improved air brake 
mechanism, pneumatic track sander, air compressor couplers, and draw-heads. 

In order to convey some idea of the relative size of these locomotives it may be 
noted that at the nominal rating of the motors, each locomotive is capable of accelerat¬ 
ing on a level a train weighing 3,000 tons with a current consumption of 2,200 amperes. 
At a speed of 13 miles per hour this current steadies down to 900 amperes. With 
the same current of 2,200 amperes the locomotive will accelerate a 1,400-ton train to 
a speed of 10 miles per hour on a 1 per cent, grade, the current at this speed 
being 1,600 amperes. The free running speed of the locomotive, without train, is 
approximately 24 miles per hour. 


314 





LOCOMOTIVES AND MOTOR CARRIAGES 

In Fig. 273 are given the tractive force and speed curves for one of these two- 
unit locomotives when all eight motors are connected in parallel, as published in 1904 


146 Metric Ton Bo/Li more oncf Ohio Locomotives ^ 

J Eight GE-65-Z3 Motors in Parallel. % y, 

^ / Turn Armot ure, 625 Vo It s ^ 

y • ^ Diameter oPwhee is 42? ^ 

O Pinion /9,Gear <5/ 5 $^ ^ ^ 

y u Height oP Locomotive on Drivers 320,000 Lbs^ ^ ^ u 

ft P _ 5 

10 "*0 
<i> </■) 

70000 

24 60000 

20 50000 

16 40000 

12 30000 

Q 20000 

4 IOOOO 

O O 

























* 

- zoo - 300 

- 180 - 800 

trn inn 












































































































































7 






















2 

7 






























- /ou — /uu 

- 140 - 600 

- 120 - 500 

- /00 _ 40 Q 

An 























































































ypeer 

f 
















2 , 















— ou 

- 300 

- 60 

- 40 ~ 200 

- 20 ~/00 

0 0 





























c f 

Wjj 






















rrj 

A 












































0 200 400 600 800 1000 1200 1400 1600 1800 2000 

Ampere5 per Locomotive 

Fig. 273. Character Curves of Baltimore and Ohio 1903 Geared Two-unit Locomotive. 

by the General Electric Co. of America and presumably calculated from factory 
tests of the motors. 


GEARED versus GEARLESS LOCOMOTIVES. 

The question of geared versus gearless motors for locomotives is one of considerable 
importance. In the first passenger locomotives employed on the City and South London 
Railway, gearless motors were installed, and are still almost exclusively employed on 
this road, the only geared locomotive being kept as a spare, and employed in shunting. 
In the locomotives used on this road, the armature is built up directly on the axles, as 
shown in Fig. 274, and no provision is made for protecting it against the blows trans¬ 
mitted through the wheels from the track. Mr. P. V. McMahon, the Chief Engineer 
of the City and South London Railway, nevertheless reports 1 that “ although troubles 
have been experienced with these locomotives, principally due to failures of armature 
winding, they have run upwards of 400,000 miles in actual service.” The average 
life of the armature works out at “ over 100,000 miles before rewinding, and experi¬ 
ence shows that in no case can the armature failures be traced to having the armatures 

1 Cassier’s Magazine, August, 1899, p. 535. 

3G 



















































































ELECTRIC RAILWAY ENGINEERING 


directly secured to the axle of the locomotive.” Mr. McMahon states that in the case 
of the only geared locomotive employed on the road, armature troubles are just as 



Fig. 274. Method of Mounting Armature on Axle of City and 
South London Railway Gearless Locomotive. 


frequent as with the gearless locomotives, “and the gearing makes such a noise that 
this locomotive is kept as a spare one and is used for shunting.” The City and South 

















LOCOMOTIVES AND MOTOR CARRIAGES 


London locomotives have been supplied by various firms. The type supplied by 
Messrs. Siemens Bros, is illustrated in Fig. 275. 

As already stated, the earlier Baltimore and Ohio locomotives are equipped with 
gearless motors. The armatures are carried on sleeves, on the ends of which spiders 
are shrunk, and the driving wheels are rotated by the spider arms which project 
between the spokes and are provided with double rubber cushions. This construction 
has been illustrated in Fig. 268 a, on p. 309, which represents a truck of one of these 
locomotives with the gearless motors in place. 

The Central London Railway Locomotives. 

The Central London locomotives, outline drawings of one of which are given in 
Fig. 276, were each equipped with four gearless motors, of the G.E. 56 type. These 
were supplied as of 117 h.-p. each, but, in accordance with the standard 1-hour method 
of rating, they could more properly be estimated as of 170 h.-p. nominal capacity each. 
For these motors, the armature cores were built up on sleeves, which were pressed 
directly upon the shaft. These moderately heavy locomotives (each weighed 44 metric 
tons), occasioned vibrations in the buildings above the tube in which they operated, 
and a geared and consequently lighter locomotive was tried. The geared loco¬ 
motive was equipped with four 150 nominal h.-p. motors (of the G.E. 55 A. 
type), the ratio of gearing being 3'3 : 1. The weight of this geared locomotive was 
oniy 314 tons, or 72 per cent, of the weight of the gearless locomotive. There still 
being some vibration, however, locomotives were altogether abandoned, and the road 
is now operated exclusively with a service of trains each consisting of five trailers at 
the middle of the train and a motor car at each end, the end truck of each motor car 
carrying two 125 h.-p. motors of the G.E. 66 A. type, with a ratio of gearing of 3‘9 : 1. 

In Table XCVIII. are given the detailed weights of the gearless Central London 
Railway locomotive :— 


Table XCVIII. 


Detailed Weights of Gearless Central London Railway Locomotive. 


Description of Part. 

Weight 

in Pounds. 

Each. 

Total. 

Platform frame ...... 


10,600 

Cab with sloping ends ..... 


2,770 

Two trucks without motor, wheels, and axles . 

9,435 

18,870 

Four motor armatures, less shaft 

3,000 

12,000 

Four motor fields ...... 

9,000 

36,000 

One controller....... 

1,808 

Thirty P.R. resistance boxes .... 

100 

3,000 

One C.P. 10 air-pump (with motor) . 

One air receiver (included in locomotive frame) 


1,280 

Small electrical accessories, say 


200 

Motor connections ...... 


115 

Brushes ........ 


76 

Eight wheels ....... 

975 

7,800 

Four axles ....... 

760 

3,040 

Total pounds . 

— 

97,559, 


or 443 metric tons. 


3D 















3 J8 


Fig. 276. Central London Railway Gearless Locomotive. 












































































































































































































































































































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 

The weights of the component parts of the locomotive, excluding electrical 
equipment, are given in Table XCIX. 

Table XCIX. 

Gearless Central London Locomotive Weights, Exclusive of Electrical Equipment. 


Description of Part. 

! 

Weight in Pounds. 

Each. 

Total. 

Platform frame 


10,600 

Cab wdtli sloping ends .... 


2,770 

Two trucks without motor, wheels, and axles 

9,435 

18,870 

Eight wheels ...... 

975 

7,800 

Four axles ....... 

760 

3,040 

Total pounds . 


43,080, 


or 19'6 metric tons. 


The weights of the electrical equipment are given in Table C. 

Table C. 

Weights of Electrical Equipment of Gearless Central London Locomotive. 


Description of Part. 

Weight in Pounds. 

Motor armatures .... 

12,000 

Motor fields 

36,000 

Controller (L.7) 

1,800 

Pressed ribbon resistances .... 

3,000 

Air compressor set . 

1,300 

Small electrical accessories .... 

200 

Motor connections and brushes 

200 

Total weight electrical equipment . 

54,500, or 


25 metric tons, or 56 per cent, of total weight of locomotive. 


Paris-0 cleans Locomotives. 

In Figs. 277 and 278 is illustrated a 49 metric ton 1 geared locomotive, somewhat 
1 irger than the Central London geared locomotive, but of the same general type. 
Eight locomotives of this design were, in 1900. placed in service on the lines of the 
Chemin de Fer de Paris-Orleans to haul 300-ton passenger trains from the Austerlitz 
Station through 2'4 miles of tunnel to the new terminus near the Quai d’Orsay. 
Most of the trains made an intermediate stop of 1 minute’s duration at Pont St. 
Michel. The running time over these 2'4 miles, including the intermediate stop, was 
8 minutes, or a schedule speed of 18 miles per hour. The express service required 
only 7 minutes, which corresponds to 20‘5 miles per hour. Each locomotive was 

1 The weight of the locomotive has often been quoted at 100,000 lbs., or 45 metric tons. The 
true figure is, however, 49 metric tons. 


319 































ELECTRIC RAILWAY ENGINEERING 



49 METRIC-TON PARIS-ORLEANS GEARED ELECTRIC LOCOMOTIVE, 















































































































































































































































































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 

equipped with four geared 250 h.-p. 1 motors of the G.E. G5 A. type, one on each axle 
of the two bogie trucks, or 1,000 h.-p. per locomotive. 

The design of the locomotive consists of a central, steel cab with sloping ends mounted 
on a channel framework and carried by two swivel trucks. The trucks are of especially 



Pig. 278. Paris-Orleans Geared Electric Locomotive. 

heavy build, being constructed with solid forged-steel side frames after the manner of 
steam locomotive construction, and in contrast with the common M.C.B. type. The 
general appearance of the locomotive is clearly shown in Figs. 277 and 278, and the 
principal data are set forth in Table Cl. 


Table Cl. 

Pi incipal Jjata of Paris-Oi leans Geared Electric Locomotives. 


Length over all . 

Width „ . 

Height above rails 
Distance between trunk centres 
Wheel base, each truck 
s) ,, total . 

Diameter drivers . 

Central cab length 
,, ,, width 

Number of driving wheels 
Total weight of locomotive 

1 These motors have been referred to as of 225 h.-p 


34 ft. 10 ins. 


9 

12 

16 

7 
23 

4 

9 

8 


7 

9 

0 

10 


>, 10 „ 

>> 1 )> 

„ 10 „ 

„ 11 „ 

8 

49 metric tons. 


therefore, taken them as being of 250 h.-p. capacity on the 1-hour basis of rating. 
E.R.E. 321 


and also as of 270 h.-p. We have, 


Y 














ELECTRIC RAILWAY ENGINEERING 


The truck side frames are carried on half-elliptic springs over each axle-box, the 
arch of the spring (which is inverted) resting on top of the axle-box, and the ends of 
the springs supporting the side frames by means of links. The bolster is supported 
on regular double elliptic springs carried in the transom. 

The motors are of the single reduction railway type, and are supported by 
nose suspension on a lip carried by the truck transom. The gear ratio is 
78 to 19 (4*1 to 1), and the axle brackets surround an axle 7 ins. in diameter, 


3 



Amperes per Locomotive 


su 

c. 

v £ 

r- 900 


L 800 
700 
600 
500 
400 
300 
■ ZOO 


too 

0 


Fig. 279. Characteristic Curves of Paris-Orleaxs Locomotive, with 

4’1 Gear Eatio. 


the size of the axle being 7*5 ins. in the gear fit and 6 ins. in the journals, 
which are 10 ins. long. The controller is of the L. 7 series parallel type, 
and is operated in conjunction with rheostats located in the sloping cab ends. 
The air brakes are of the Wenger compressed air system, the supply being 
furnished on each locomotive by a pair of C.P.-10 compressors, each having 
a rated piston displacement of 35 cubic ft. per minute against 90 lbs. per square 
inch. The track sanding device and the whistle are operated from the compressed 
air supply, which is maintained at constant pressure by means of an automatic 
governor operating in connection with the compressor motors. Included in 

322 





























































5 

S 

V. 

<u 

v> 

64 

56 

48 

40 

22 

24 

/6 

8 


1 

£ 

4o 

V> 

VS 


Ear/ s - Or!eans tocomob/ ye 

four Gr. E. 65 -A Motors in PataII d 
/ Turn Armature. 500 /olbs 
JJiamcber of b/beds 49 " 


LOCOMOTIVES AND MOTOR CARRIAGES 

the electrical equipment of the locomotive are also an ammeter, volt meter, and 
recording watt meter, together 

with a main circuit breaker, . c 

magnetic blow-out, main switch, 
and other accessories. 

The third-rail system sup¬ 
plies current at 575 volts, and 
the locomotive is equipped with 
four shoes for making contact 
with the side running conductor. 

In certain portions of the route 
where the track work is difficult, 
the side rails are supplemented 
by short stretches of rail in the 
centre, for which the locomotive 
carries suitable additional contacts 
supported by insulated brackets 
on the motor frames. At still 
other points where undesirable 
complication in the third-rail 
arrangements has been expe¬ 
rienced, the current is now fed 
to the locomotive b}^ an over¬ 
head conductor of inverted 
T-iron, and the top of the cab 
is provided with a parallel 
motion shoe which comes into 
requisition at these points. 


14000 
/ zooo 
ioooo 
8000 
6000 
4000 

2000 

0 
































































































.t 



















A 

=7 





































is 


















1 





















V 





















3 
























rV 




























































































































.e 


V 

s- 

L 

v> 



.c 

< 

V 

£ 


•5 

:f 

v 





> 

V 

* 

<0 


■400 

■3SO 

■500 


SO 

o 


- 000 
-8 00 
1-7 00 
, -600 
-500 

i 

-400 
-300 
-200 
-100 
I- 0 


Amperes per 


Locomot/re 


Fig. 280. Characteristic Curves of Paris-Orleans 


Electric Locomotives with 2-23 Gear Ratio. 
I he w eight of the electrical equipment is made up as shown in Table CII. 


Table CII. 


Weights 


of Electrical Equipment of Paris-Orleans 


Geared Electric 


Four G.E. 65 A. motors, including gear and gear case, at 8,930 lbs. each . 
A eight of rheostats per locomotive ....... 

A eight of controllers per locomotive ....... 

Weight of remainder of electric equipment....... 


Locomotives. 

35,700 

3,000 

4.500 

3.500 


1 ottil weight of electrical equipment of one locomotive, including motors, 
controllers, rheostats, gearing, air compressors, and instruments . . 46,700 lbs., or 

21 0 metric tons, or 43 per cent, of total weight of locomotive. 


The initial equipment furnished to the Orleans Co. comprised eight complete 
locomotives, each of which made an average total of over 18,000 locomotive miles per 
annum, the crow-mileage totalling for the same period about 10,500 locomotive miles. 

The Paiis-Orleans road has since 1900, when these eight electric locomotives 
were put in service on the ‘2’4-mile tunnel section, gradually carried out the electrifica¬ 
tion of other sections of the line. Chief among these is a 1‘2-mile section between 
Austerlitz fetation and Juvisy. This necessitated more rolling stock; and, in addition 
to securing three new locomotives and a number of motor cars, the company, in 1904, 

323 Y 2 













































































KEM 


ELECTRIC RAILWAY ENGINEERING 


changed the gear ratio of seven of these eight original locomotives from 4‘1 to 2‘23, thus 
changing the characteristic curves from those shown in Fig. 279 to those of Fig. 280. 

The three new locomotives are of the “ baggage-car ” type, as shown in Fig. 281. 
Each new locomotive is also equipped with four G.E. 65 motors with a gear ratio of 
2*23, and therefore also has the characteristics shown by the curves of Fig. 280. 

Denoting by E 1 that one of the eight original locomotives which still has the 
original gear ratio of 4*1, by E 2 to E 8 , those in which the ratio has been changed to 
2*23, and by E 9 to E 11 , the new locomotives of the “baggage car type,” we obtain the 



leading data set forth in Table CIII. The figures in the last column, AE 1 to AE 5 , refer 
to five motorcars each equipped with four G.E. 66 motors. These motors each have a 
1-hour rating of 125 h.-p. 


Table CIII. 


Data of Paris-Orleans Rolling Stock. 



Original Type (190G). 

Baggage Car 
Type (1904). 

Motor Cars. 


El. 

E2 to Eg. 

Ey to Ell. 

AEi to AEj. 

Weight ...... 

49 tons. 

49 tons. 

55 tons. 

45 tons. 

Length over all 

34 ft. 10 ins. 

34 ft. 10 ins. 

37 ft. 6 ins. 

57 ft. 0 ins. 

Number of bogies 

2 

2 

2 

2 

Wheel base, each truck 

7 ft. 10 ins. 

7 ft. 10 ins. 

7 ft. 10 ins. 

6 ft. 6 ins. 

Distance between truck centres 

16 ft. 0 ins. 

16 ft. 0 ins. 

18 ft. 6 ins. 

40 ft. 8 ins. 

Diameter drivers 

4 ft. 1 in. 

4 ft. 1 in. 

4 ft. 1 in. 

3 ft. 6 ins. 

Ratio of gearing .... 

4-1 

2-23 

2-23 

3-08 


324 












































LOCOMOTIVES AND MOTOR CARRIAGES 

The locomotives with the 2’23 gearing, when running without a train, may attain 
a speed of 62 miles per hour, and will haul a 200-ton train at a speed of 43 miles per 
hour.. Each locomotive is supplied with an extra controlling switch permitting of 
giouping the four motors either in two groups of two motors in series or in two groups 
of two motors in parallel. The main controller effects the series-parallel controlling 
of these two groups. The newest locomotive is furnished with multiple unit control 
apparatus, but the first ten locomotives have L. 7 controllers. 

Tvo motoi cais, each equipped with four G.E. 66 motors, when employed in a 
train of a total weight of 200 tons, cover the 12 miles from Austerlitz to Juvisy in 
15 minutes without a stop. This is an average speed of 48 miles per hour from start 
to stop. Some still never motor cars are furnished with G.E. 55 motors, and the 
first five motor cars will ultimately have their G.E. 66 motors replaced by G.E. 
55 motors. 

Gearless Locomotive t'.specially adapted to Heavy Traction at High Speeds. 

The contractors for the New York Central locomotives, in referring to this 
question of geared versus gearless locomotives, have stated that, in studying the condi¬ 
tions to be met by the New York Central locomotives, it was concluded that the gearless 
motor design possessed characteristics especially adapted to high speed electric traction 
work. For the specified service conditions it was thought to be superior to any geared 
motoi which it was possible to build. In working out the design, the endeavour was 
to secure great simplicity, strength, ease of inspection, and facility in making repairs. 
The absence of motor bearings and gears and the excellent commutation and heating 
qualities of the motors are stated to ensure minimum maintenance charges. In 
making lepaiis oi renewals, an armature, with its wheels and axle, may be removed 
by lowering the complete element without disturbing the fields or any other part of the 
locomotive, and a new element inserted in its place. The design overcomes the great 
difficulty of providing a sufficiently small clearance between pole shoes and armature 
surface, and at the same time permits sufficient flexibility of support to the magnet 
frame to prevent unduly severe blows on the track. By the choice of a two-pole 
construction, a large vertical movement of the spring-borne frame does not materially 
affect the depth of the air gaps. In the design of the New York Central locomotive, the 
dead weight on the axle is not materially greater than is customary with locomotives, 
and, furthermore, there is no unbalanced weight to produce vibration, with attendant 
injury to the track and road-bed construction. Table CIV. was prepared in this 
connection to show the estimated total dead weight per axle of the electric locomotive 
shown in Fig. 252, as compared with representative steam locomotives of equal 
capacity:— 

Table CIV. 


Comparison of Steam Locomotive with Gearless Bi-polar Electric Locomotive. 



Total Weight 
of Driving 
Wheels—■ 
Pounds. 

Diameter 

Driving 

Wheels. 

Total Dead Weight 
per Axle—Pounds. 

Unbalanced 
Dead Weight per 
Axle—Pounds. 

Steam locomotive 

131,000 

51 ins. 

7,000 to 11,000 

122 to 129 

>? >> ... 

127,500 

70 ins. 

10,000 to 13,000 

77 to 81 

Electric locomotive of Fig. 252 

133,000 

44 ins. 

12,000 

0 


325 















ELECTRIC RAILWAY ENGINEERING 


Advantages Associated with the Greater Weight of Gearless Locomotives .— 

Adhesive Coefficients. 

Furthermore, the use of gearless motors on locomotives is often of distinct 
advantage in giving the weight per axle necessary for securing sufficient adhesion in 
starting heavy loads. In some cases, where geared motors are used on electric loco¬ 
motives, it has either been the practice to adopt an especially heavy truck construction 
or to load the locomotive with ballast. It must, however, be borne in mind that, owing 
to the exceedingly uniform effort imparted to the driving wheels by the rotative motion 
of the armature as compared with the varying thrust of a steam locomotive, an electric 
locomotive of a given weight can exert a greater tractive force before slipping the 
wheels than can a steam locomotive. It is on record that the 87-ton gearless Baltimore 
and Ohio locomotive has started from rest a 1,700-ton train against such a grade as to 
require the development of a tractive force of 63,000 lbs. behind the locomotive, which 
thus developed a tractive force of 720 lbs. per ton of weight. This is a tractive force 
equal to over 32 per cent, of its weight. Of course in such tests the condition of the 
track is of great importance ; nevertheless, it is common in steam locomotive practice 
to estimate on not over half this amount of adhesion. A value of 25 per cent, may safely 
be employed for the adhesive coefficient in the case of electric locomotives, as 
against some 16 per cent, for steam locomotives. 

In a paper read before the Pacific Coast Railway Club, 1 McDoble has touched 
upon this subject. His estimations of the adhesion coefficient in the case of steam 
and electric locomotives respectively, are set forth as follows :— 

“ From 25 to 30 per cent, of the weight of an electric locomotive can be utilised 
as draw-bar pull, while actual tests have shown that as high as 33 per cent, can be so 
used. Compared with these figures are coefficients ranging from only 13 to 16 per 
cent, for the most powerful steam locomotives built. These figures are based on the 
ratio of the maximum draw-bar pull to the total weight of the locomotive. Con¬ 
sidering the comparative weights on the drivers in each case, we find that the 
electric locomotive shows an increase over the steam, of from 10 to 20 per cent.” 

Carter, 2 however, makes the most explicit statement, and one which the authors 
feel inclined to regard as the most sound. He states : — 

“ The weight on driving wheels must be determined before the equipment can be 
finally settled upon, in order to discover whether the adhesion is sufficient to stand 
the tractive effort of the motors. The accelerating tractive effort should not exceed 
about 17 per cent, of the weight on driving wheels in the case of trains driven by 
motor cars, operated by the multiple-unit system of train control, wherein it is 
impracticable to sand the rails in front of all driving wheels in bad weather. Where 
locomotives are used, however, the average accelerating tractive effort may be allowed 
to amount to 24 or 25 per cent, of the weight on driving wheels, if efficient provision 
is made for sanding the rails in case of need.” 


The Valtellina Three-Phase Gearless Locomotives. 

The polyphase motors supplied by Messrs. Ganz & Co. for the Valtellina Railway, 
have also been of the gearless type, or rather they have all had a speed equal to that 

1 Electric Journal, August, 1905. 

2 “ Technical Considerations in Electric Railway Engineering,” paper read before the Institution 
of Electrical Engineers, January 25tli, 1906. 

326 


LOCOMOTIVES AND MOTOR CARRIAGES 


of the driving wheels, although, as we shall see, the motor, in the latest design of 
locomotive, transmits its power to the driving wheels through a connecting rod. This 
arrangement overcomes the necessity for mounting the armature directly upon the 
driven axle, and introduces further obvious advantages as regards better utilisation of 
the available space. 


First Valtellina Electric Locomotives. 

The first locomotives, as illustrated in Fig. 282, were, however, of the true gearless 
type with the armatures on the driven axles. Each locomotive was equipped with four, 



Fig. 282 . Early Type of Valtellina Three-Phase Gearless Locomotive. 


three-phase induction motors. The locomotives were mounted on bogie trucks with 
wheels of 55 ins. diameter, and were equipped with four gearless motors, each of 
225 h.-p. rated capacity. As the locomotives were designed for freight haulage at a 
constant speed of 18’6 miles (30 kilometres) per hour, cascade control w 7 as not 
provided. When it is desirable, with these locomotives, to run the train at a speed 
lower than normal, resistance is inserted in the rotor circuit. It is further arranged 
that all the motors or only a part of them may be used, according to the load. The 
four liquid starters are so constructed that the water level is always the same in all of 
them, and any level can be maintained for any required time. 

These locomotives weigh 47 metric tons. Each motor weighs 4'9 metric tons and 

327 
























ELECTRIC RAILWAY ENGINEERING 


runs at a speed of 128 revolutions per minute, corresponding to 14 poles and 
15 cycles per second. Drawings of this locomotive are given in Figs. 283, 284, 
285, and 286. 


Valtellina Electric Locomotives of 1904. 

These new locomotives for hauling passengers, express freights, and ordinary 
freights, have also been supplied to the Valtellina Railway by Messrs. Ganz & Co. The 


-~~ —H—^-H 



Fig. 285. 


Early Type of Valtellina 


!2S 


(Gearless) Locomotive. 



























































































































































































































































Fig. 283. Early Type of Valtelliya (Geaeless) Locomotive. 















































































































































































































































































































































































































































































































































































































Fig. 2S4. Early Type of Valtellina (Gearless) Locomotive 





































































































































































































































































































































































































































































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329 

































































































































































































































































ELECTRIC RAILWAY ENGINEERING 

design of these locomotives differs radically from that employed for the first "\ altellina 
locomotives. In the first place, they are proportioned for considerably higher speed 
and power, and weigh 6*2 metric tons, as against the 47 tons weight of the first 
locomotives. 

The specification to which these 1904 locomotives were required to conform, called 
for two normal speeds, the first being from 37 to 43 miles per hour, and the second 
from 18*5 to 21*5 miles per hour. The required tractive force at the rim of the driving 
wheels is equal to 3*5 metric tons at the higher, and 6*0 metric tons at the lower of 
these speeds. Each primary motor, when operated at its normal speed of 2*25 
revolutions per minute, has a nominal (1 hour 75 degrees Cent.) rating of 600 h.-p.; 
hence the nominal rating of a locomotive at its standard full speed is 1,200 h.-p. 



Fig. 287. “1904” Type of Valteleina Locomotive. 


For half-speed the rotors of the primary motors feed the stators of the cascade 
motors, and the two pairs of motors then have a nominal 1-hour rating of 900 h.-p., 
or 450 h.-p. per pair of motors. They are required to accelerate a 400-ton train on 
an incline of 0*1 per cent, in 55 seconds from rest up to a speed of 18 6 miles per 
hour. They are also required to accelerate a 250-ton train on an incline of 0*1 per 
cent, from rest to a speed of 37 miles per hour in 110 seconds. These performances 
correspond to tractive forces some 50 per cent, higher than those given above as 
normal. Taking the first of these two specified performances, and assuming a uniform 

18*6 

rate of acceleration, this works out at -=-r- = 0*34 m.p.h. per second. This would 

o o 

require a tractive force of 34 lbs. per ton. The 0*1 per cent, incline would call for a 
further 2*2 lbs. per ton, or a total of about 36 lbs. per ton. The train, together with 
the locomotive, weighs 400 —J- 62 = 462 tons, and thus there is required to be 

330 


















LOCOMOTIVES AND MOTOR CARRIAGES 

developed at the rims of the driving wheels a tractive force of 462 X 36 = 16,700 lbs. 
For the second specified performance, the rate of acceleration is again 0‘34 m.p.h. 



33i 







































































































































































































































































ELECTRIC RAILWAY ENGINEERING 


per second, and since the grade is again 0*1 per cent., the tractive effort is 
(250 -f- 62) X 86 = 11,200 lbs. But this must be exerted for 110 seconds as 
compared^with 55 seconds during which the 16,700 lbs. tractive force were called 
for. These tests were required not only at the normal pressure of 3,000 volts, 
but also at 2,700 volts. It was also required that the locomotive should be able to 
start a 250-ton train on a 2 per cent, grade and bring it up to a speed of 18*6 miles 
per hour. 

It was required that the motors and electrical apparatus should be so constructed 
that every 2 minutes for 1 hour they should be capable of starting a 400-ton train 

on a 0*3 per cent, grade, and of bringing it up 
to a speed of 18*6 miles per hour, without 
excessive heating. 

A further requirement was that the motors 
should be so designed that on a 10 hours’ 
test in the shops at each of the normal speeds 
and loads the temperature rise of no part 
should exceed a temperature of 60 degrees 
Cent, above the surrounding air. They should 
also stand a 100 per cent, overload for 200 
seconds without more than 40 degrees Cent, 
temperature rise above surrounding air, and 
a 50 per cent, overload for 1 hour for this 
same limiting temperature increase. 

A feature of especial interest relates to 
the means by which the power is transmitted 
from the motors to the driving wheels. The 
coaxial arrangement has been entirely aban¬ 
doned with a view largely to facilitating ready 
access to the motors for repairs or general 
attention. The motors are mounted between 
the driven axles, and act on a connecting rod by means of cranks. A photograph 
of one of these locomotives is given in Fig. 287, and drawings will be found in 
Figs. 288 to 293. A photograph of the interior of the driver’s cab is given in 
Fig. 294. A diagram of the electrical connections is given in Fig. 295. 

The bearing by which the crank on the middle driving wheel communicates with 
the connecting rod is, as shown in Fig. 296, designed so as to have a free vertical 
movement. This is necessary in order to prevent any vertical vibration from being 
transferred from the wheels to the rotor. It also protects the rails from variable 
pressures due to the reciprocating parts. 

The locomotive has a total weight of 62 tons, of which 42 tons come on the driving 
wheels. The total length of the locomotive is 38 feet; the wheel base between each 
two driving wheels is 7*7 feet. The driving w'heels have a diameter of 59 ins. 
Instead of having four separate motors, as in the first locomotives, one high tension 
(3,000 volts) and one low tension (400 volts) motor have been combined in a single 
casing. Each is wound for 8 poles, and therefore at 15 cycles the normal speed is 225 
revolutions per minute. When connected in cascade, the speed is 112*5 revolutions 
per minute. The low voltage motors are not in circuit at the higher speed. The 
normal speed of the locomotive is 40 miles per hour when the primary motors are alone 
in circuit, and 20 miles per hour for cascade operation. Each motor frame is supported 

332 



Fig. 289. “ 1904” Type Valtellina 

Three-Phase Electric Locomotive. 








































































































LOCOMOTIVES AND MOTOR CARRIAGES 



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291. 1904 Type Valtellina Three-Phase Electric Locomotive. 











































































































































































































































































































































ELECTRIC RAILWAY ENGINEERING 





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Fig. 292. “1904’’ Type Valtellina Three-Phase Electric Locomotive. 


































































































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 

by four rods with spiral springs between the heads and the lugs on the frame. A 
photograph of one of the combination cascade motors is given in Fig. 297, and drawings 
in Fig. 298. The novel arrangement of the collector rings, as clearly seen in Figs. 297 
and 298, is a noteworthy feature. The slip rings are only in circuit when the primary 
motor is alone in service. For cascade connection, the current from the windings of 
the primary rotor flows directly to the windings of the low voltage rotor. Carbon 
brushes are employed with the slip rings. A view of the slip rings with the brushes in 



Fig. 293. Trolley for “ 1904” Type Valtelliya Three-Phase Electric Locomotive. 

place is shown in Fig. 299. Each primary motor alone would weigh 8'2 metric tons, 
but the secondary motor brings the combined weight up to 12*4 metric tons. Hence the 
total weight of the two combination sets of motors amounts to 24’8 metric tons. The 
motors therefore constitute 40 per cent, of the 62 metric tons of total weight of the 
complete locomotive. Each of the two bogie trucks carries one of these combined 
primary and secondary motors. 

Of the three locomotives supplied, two are equipped with liquid starting rheostats, 
and one with metallic starting rheostats. The entire control, including the manipulation 

335 












































ELECTRIC RAILWAY ENGINEERING 


of the trolley and of the water rheostats, is effected by means of compressed air. 
Diagrams of the pneumatic connections are given in Figs. 300 and 301, relating respec¬ 
tively to arrangements with water and metallic rheostats. The controller is provided 
with such interlocking connections that the motors can only be reversed when the 
primary circuit is open. 

The photograph in Fig. 302 illustrates the motor-driven air compressor. The 



Fig. 294. Interior of Driver’s Cab of “ 1904” Valtellina Locomotive. 


motor is supplied from the 110-volt secondary of a 5-kilowatt oil transformer, whose 
primary windings are fed at 3,000 volts. At its normal speed of 430 revolutions per 
minute, this compressor can supply 520 litres 1 of air. Two air receivers, located on 
the roof of the locomotive, are provided. One of these supplies air for the electrical 
apparatus, and the other for the Westinghouse brakes. The compressor motor is cut 


1 This volume corresponds to atmospheric pressure. 

336 
























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l'ig. 296. Communicating Bearing between Crank and Connecting Bod on 
“ 1904” Type Valtellina Three-Phase Locomotive. 



Fig. 297. One op the Cascade Motor Sets of the “ 1904” Ty t pe Valtellina 

Three-Phase Electric Locomotiye. 


E.R.E. 


337 


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ELECTRIC RAILWAY ENGINEERING 


in and out automatically, according as the pressure in the receivers falls below or rises 
above a pressure of six atmospheres. Place was originally provided on the locomotive 
for a second step-down transformer and air compressor, and these have subsequently 
been installed. 

The locomotives are operated from a three-phase line at a periodicity of 15 cycles 
per second, and a pressure of 3,000 volts. At the power-house the energy is supplied 
direct from 20,000-volt generators, and is transmitted at this pressure to sub¬ 
stations, where it is reduced in stationary transformers to 3,000 volts, and delivered to 



Fig. 299. Showing Slii> Rings of Motor of “1904” Type Yaltellina Three-Phase 

Electric Locomotive. 

the low tension conducting system, which consists of two overhead wires and the track 
rails. All the three locomotives are in regular service hauling 250-ton passenger and 
400-ton freight trains. 


Regenerative Features as observed at Valtellina. 

Cserhati ( Zeit . T er. Dent. Ing. XLVIII., pp. 125—132, January 28th, 1905) has 
pointed out an interesting feature observed on the Yaltellina road. It is found that, in 
spite of the relatively infrequent service of heavy trains, the fluctuations in the load 
at the power-house are relatively small. Thus for the entire day, the maximum 
load is only three times the average load, and if one deducts those hours during 
which only a single train is running, and for which a single generating set suffices, 
and considers only the remaining part of the day, then the maximum load is only 

338 


















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LOCOMOTIVES AND MOTOR CARRIAGES 


1'8 times the average load. Now the generators are driven by water power, and the 
speed regulation is none too good. This, however, is the basis of the advantage to 
which Cserhati calls attention, namely, that, should several trains start up at once, the 
drop in speed of the generating sets is so great that the induction motors of the trains 
running at normal speed at the time, act as generators, and feed back into the line, 
and, in fact, pull the power-house generators up to speed again. Thus extreme peaks 
of load are avoided. Cserhati describes the trains on the line as constituting the 
equivalent of a gigantic fly-wheel which materially decreases the overload shocks on the 



Fig. 302. Motor-driven Air Compressor for the “ 1904” Type Valtellina 

Three-Phase Electric Locomotive. 


power-house plant. The relatively low amount of power required is stated to he also 
in part due to the smooth starting rendered practicable by the use of water rheostats. 

1906 Ganz Locomotive Supplied to the Italian State Railways. 

On an order for the Italian State Railways, Messrs. Ganz & Co. have now (1906) 
just completed two new three-phase high tension locomotives. One of these is shown 
at the International Simplon Exhibition at Milan. This new type of locomotive is, 
as regards its mechanical parts, similar to the three electric locomotives last supplied 
by Messrs. Ganz & Co. for the Valtellina Railway, and only differs from them in the 
electrical equipment in so far that, instead of having twin motors, it is equipped with 
two single motors, which are disposed in the locomotive similarly to the twin motors of 
the previous locomotives. Both motors are high tension motors, one having eight 
poles, the other twelve poles, and the independent connection of these motors and the 
cascade connection of both allows of the use of three economical speeds corresponding 
to the number of poles, i.e., eight, twelve, and twenty, thus permitting of speeds of 
64, 424, and 25 kilo-metres per hour. The rated capacity of the motor with eight 

341 




ELECTRIC RAILWAY ENGINEERING 



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LOCOMOTIVES AND MOTOR CARRIAGES 


poles is 1,500 h.-p.; that of the twelve pole motors is somewhat smaller. Valatin has 
kindly informed the authors that the 1,500 h.-p. motor weighs 13*1 metric tons. Its 
synchronous speed is 225 R.P.M. 


Valtellina Motor Cars. 

The original equipment of electrical rolling stock for the Valtellina Railway also 
comprised ten motor cars for passenger traffic. Each motor car weighs 53 tons, and 
generally hauls five coaches, the total weight of the train being 150 tons. A drawing 
of one of the motor cars is given in Fig. 303. The trains have two economical running 
speeds, a speed of about 40 miles 
per hour employed for the main 
journey of express passenger 
trains, and a speed of 20 miles 
per hour employed when running 
through stations or up heavy 
inclines. The lower speed is 
also used for local trains. The 
cascade system of control is em¬ 
ployed for obtaining these two 
speeds. Each car has four 
motors, of which two are wound 
for 3,000 volts, and two for the 
lower pressure of 300 volts. Each 
of the four motors weighs 3‘8 
metric tons. Each series pair of 
these motors develops 150 h.-p. 
in cascade connection, i.e., at half¬ 
speed. At full speed, the high 

tension motors alone are able 
to develop 150 h.-p. at their 
normal speed of 300 revolutions 
per minute. The rated capacity 
of each motor on the one hour 
75 degrees Cent, basis is 250 h.-p. 

They are able to give 150 h.-p. 
during 10 hours without heating more than 45 degrees Cent., and in actual working 
they are also loaded up to 300 h.-p. 

The motors are gearless, transmitting their power to the spokes of the wheels by 
means of elastic couplings. Figs. 304 and 305 show this coupling, which is intended 
to allow the rotor to run uniformly even when the wheels are subjected to severe con¬ 
cussions. The rotor laminations are mounted on a hollow shaft, concentric with the 
train axle. The maximum clearance between the two concentric shafts is If ins. 
Bogie trucks are used, and their construction may be seen from Fig. 306. 

A feature of the motor construction, to which attention may well he drawn, is that 
the lower part of the stator is flattened off. This allows a larger motor to be used with 
the 46-in. driving wheels than would otherwise have been possible. In the control of 
the motor cars, compressed air has been used to a very great extent. An air-pump 
is driven by a 4 h.-p. motor. The pressure in the air-pump is about six metiic 

343 



Fig. 304. TmiEE-PnASE Motor Mounted on Axle of 
Valtellina Motor Carriage. 








ELECTRIC RAILWAY ENGINEERING 


atmospheres, and is regulated automatically. Provision has been made for hand 
regulation in case of failure of the automatic control. The compressed air is used 
for the following purposes:— 

(1) Switching the primary circuit on and off; 

(2) Operating the Westinghouse brakes ; 

(3) Piaising the trolley ; 

(4) Controlling the liquid starter and the whistle. 

It is stated that the experience on the Yaltellina road has shown electric locomo¬ 
tives to be preferable to motor cars. Both electric locomotives and motor cars are 



Fig. 305. Elastic Coupling between Wheel and Motor of 
Yaltellina Motor Carriage. 


employed on this road, and the average yearly mileage has amounted to 34,000 miles 
per electric locomotive or motor car, as against a yearly average mileage of only 
17,000 miles per steam locomotive on the entire Adriatic line of which the Yaltellina 
line is one section. This advantage of two to one in favour of the electric locomotives and 
motor cars is stated to be largely due to the absence of the steam boilers, the attendance 
and repairs on which are stated to be the chief causes for the large amount of time 
that the steam locomotives are out of service. The higher average speed of the 
electric trains must also have contributed considerably to the higher annual mileage 
per electric locomotive and motor car, as also the greater ease of manipulation in 
shunting, etc. There is evidently so great an advantage in this respect, that a much 
smaller percentage of spare locomotives should afford equal security of uninterrupted 
maintenance of the traffic with electric than with steam service. 

Incidentally we may mention an advantage of electric locomotives over motor 

344 






















































LOCOMOTIVES AND MOTOR CARRIAGES 

cars. The heating of the motors limits the output of a modern electric equipment on 
continuous service. Obviously, a much higher output can be maintained for a short 



Fig. 306. One of the Bogie Trucks of a Yaltellina Motor Carriage, with 

Three-Phase Motors. 



Fig. 307. Oerlikon 15,000 Volt, 15-Cycle Locomotive equipped with 
Single-Piiase Commutator Motors. 


time. A locomotive may lay over after some heavy work, its place being taken by a 
fresh locomotive. This would be impracticable with the passenger cars of trains making 
a long journey. 


345 






















f 



/ 


308. Oerlikon 15,000-volt 15-Cycle Locomotive, equipped with Single-Phase 

Commutator Motors. 























































































































































































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 


Oerlikon 15,000 -volt, Fifteen-cycle Locomotive, Equipped with Single-phase Commutator 

Motors. 

In this single-phase locomotive, as in the latest Ganz three-phase locomotives, the 
motors ultimately deliver their power to the driving wheels through cranks and con¬ 
necting rods, but, unlike the Ganz equipments, the Oerlikon motors also have speed 
reduction gearing. This may be seen from the photograph in Fig. 307, and from the 
drawings in Figs. 308 and 310. The periodicity is 15 cycles per second, and the trolley 
pressure is 15,000 volts. The current is collected at this high pressure by the standard 
Oerlikon collecting device, which may be seen in the above illustrations, and also in 
Figs. 318 to 321, given on pp. 352 to 354, in connection with the description of another 
type of Oerlikon locomotive. The 
current collected at the trolley is 
next carried through two air-cooled 
transformers located at the middle 
of the locomotive. These are of the 
dimensions shown in Fig. 309, and 
serve to reduce the potential from 
15,000 volts to 600 volts. Each has 
a capacity for delivering 200-kilo¬ 
volt-amperes continuously. The 
secondary winding is divided into 
twenty equal sections, there thus 
being 30 volts per section. 

The equipment comprises 
two single-phase commutator 
motors, with a rated capacity of 
200 h.-p. each, at a speed of 650 
revolutions per minute. The 
motor, which has eight main poles 
and eight auxiliary reversing 
poles, is illustrated by the 
drawings in Fig. 310, and by 
the photograph in Fig. 311. A 
diagram illustrative of the prin¬ 
ciples of operation of this type 
of motor is given in Fig. 312, from D.R.P. No. 30,388. As built, however, these 
principles were only partly incorporated. The compensating winding, for instance, 
threaded through apertures in the main poles, is omitted. In Fig. 313 is given the 
connection diagram of the wiring of this locomotive. The curves in Figs. 314 and 315 
are plotted from test results obtained on the motors. At the normal speed of 650 
revolutions per minute, the motor runs at nearly three times its synchronous speed 
for 15 cycles per second. The gear ratio is 1 to 3*1. The air compressor is driven by 
an additional 6 h.-p. 500 revolutions per minute single-phase commutator motor 
supplied at a pressure of 240 volts. The compressed air is stored up in two receivers 
at a pressure of from 6‘5 to 7'0 atmospheres, and is equipped with automatic control. 
The lighting at 15 cycles is thoroughly satisfactory, owing to the use of 20-volt lamps, 
which therefore have such a stout filament as to remain at practically constant 
incandescence in spite of the low periodicity. 

347 



Fig. 309 


Outline Drawings of 200 Kilovolt Ampere 
Air Blast Transformer of which two are 
Installed on the Oerlikon 15,000 Volt, 15-Cycle 
Locomotive with Single-Phase Commutator 
Motors (Dimensions in Millimeters). 































































































ELECTRIC RAILWAY ENGINEERING 


The total weight of the locomotive is 43 metric tons. Some of the itemised 
weights are given in Table CV. 


Table CV. 


Itemised Weights of Oerlikon 15,000-t'o^ Fifteen-cycle Locomotive, with Single-Phase 

Commutator-Motors. 


Cab and two bogie trucks ...... 

Electrical equipment and brake equipment 
One motor, exclusive of gearing . . . . 

Speed-regulating switch, complete in tank of oil 


23 - 5 tons. 
16-5 „ 


Some runs were made with this locomotive hauling a 200-ton train, and it was 
shown that not only during starting with this load, but also during running at a speed 



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Fig. 310. 200 h.-p. Single-Phase Commutator Motor with Reversing Poles as Installed 

on the 15,000 Volt, 15-Cycle Oerlikon Locomotive. 

34 § 






































































































































































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 



Fig. 311. 200 ir.-p. Single-Phase Commutator Motor with Reversing Poles, 
as Installed on the 15,000 Yolt, 15-Cycle Oerliicon Locomotive. 


i 



Fig. 312. Diagram oe Principles oe Opera¬ 
tion of 200 h.-p. Single-Phase Inter¬ 
pole Commutator Motors oe the Type 
Employed on the Oeblikon 15,000 Yolts, 
15-Cycle Locomotive. 


349 


























Jig. 313. Connection Diagram of Wiring of Oerlikon 15,000 Volt, 15-Cycle 
Locomotive with Single-Phase Commutator Motors. 


A = Collecting device. 

1! = Overhead trolley wire. 

C = Horn lightning arrester. 

I) = Multiple cap lightning arrester. 

K = Choking coil. 

F = Circuit closer to single-phase commutator motor. 

G = 230 k.w. transformer — transforming from 15,000 
volts primary to 600 volts secondary. 

II = Potential regulator. 

./ = Low tension main switch. 

K = Induction regulator for + 150 volts and 600 amperes 
L = Reversing switch for induction regulator. 

M = Lamps in motorman’s compartment. 

N = Heating coil. 



Fig. 314. Characteristic Curves of Oerlikon 
200 h.-p. Single-Phase Commutator Motor 
(Current Constant at 200 Amperes). 

V = Terminal voltage. 
n = Speed in revs, per minute. 
cos<p = Power factor. 

7 ? = Efficiency. 


0 = Voltmeter for 700 volts. 

P = Low tension main ammeter. 

Q = 50 ampere ammeter in air pump motor circuit. 

It = 900 ampere ammeter in low tension main circuit. 

.S' = Lamps in compartment containing the apparatus. 

T = 200 h.-p. single-phase commutator motor for 300 
volts, 15 cycles. 

U = Single-phase commutator motor for 120 volts for 
driving air pump. 

V = Air pump. 

W = Lamps on the side walls of the locomotive. 

X = Automatic regulating switch for motor driving 
air pump. 

Y = Pneumatic overload circuit breaker. 



Fig. 315. Characteristic Curves of Oerlikon 
200 h.-p. Single-Phase Commutator Motor 
(Speed Constant at 650 r.p.m.). 

V = Terminal voltage. 
n = Speed in revs, per minute. 
costp = Power factor. 

7? = Efficiency. 

A = Current in amperes. 


350 




































































































































































































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 

of about 25 miles per hour on an upgrade of 0*3 per cent., there was no sparking at the 
commutator. 

With the motors in series, the starting current for this load was about 1,000 
amperes in the motors. It was about 780 amperes when running up a grade of 
0-8 per cent, with this load, at a speed of 17 miles per hour, and with 450 volts at the 
motors. 


Oerlikon il lotor-generator Type of Single-phase Locomotive until Continuous-current 

Driving Motors. 

Prior to the construction of the above-described single-phase locomotive, with 
single-phase commutator motors, the Oerlikon Co. had been developing a single¬ 
phase system of traction in which the locomotive is equipped with a motor-generator 



Fig. 310. Oerlikon High-Voltage Single-Phase Locomotive of the Motor 

Generator Type. 


set comprising a single-phase motor directly connected to a continuous-current gene¬ 
rator, from which continuous-current motors driving the axles are supplied with power, 
ihe s}stem is often designated as the Ward-Leonard system. Some years ago 
H. Ward-Leonard clearly promulgated the proposition to 

“ Vary the voltage as the speed desired, 

Vary the current as the torque required.” 

A photograph of a single-phase Oerlikon locomotive of this type is shown in 
Fig. 316. This locomotive is designed for a continuous output of 400 h.-p. and for a 
speed of 37 miles per hour. Fig. 317 contains drawings of this locomotive showing 
the outlines of the motor-generator set, located in the body of the locomotive and of 

35i 









ELECTRIC RAILWAY ENGINEERING 


the two continuous-current motors, which communicate their power, first through single 
reduction gearing and then through cranks and connecting rods, to the driving wheels. 




































































































































































































Fig. 319. Oeelikox Trolley. 

















ELECTRIC RAILWAY ENGINEERING 

In types for higher speeds, the reduction gearing is omitted. The current is collected 
from the overhead wire at any voltage up to 15,000 volts, by the Oerlikon overhead 
trolley, shown in Figs. 318 to 322. For trolley pressures below 6,000 volts, the 
current is then led to a single-phase motor, generally of the non-synchronous type. 
For pressures of 6,000 volts and upwards, a step-down transformer is carried on the 
locomotive, the stator of the single-phase motor being wound for low potential corre¬ 
sponding to the secondary winding of the step-down transformer. A secondary 
pressure of 700 volts has generally been employed by the Oerlikon Co. in such 
cases. 

The locomotive illustrated in Figs. 316 and 317 has a weight of 44'1 metric tons 



Fig. 321. Oerlikon Trolley. 


when the single-phase motor is wound for the full line potential. Of this weight the 
electrical equipment constitutes 25*1 metric tons. When a transformer is employed 
in order to step down from 15,000 volts to 6,000 volts, the weight of the electrical 
equipment is increased to 27'7 metric tons, and the complete weight of the locomotive 
is then 46‘7 metric tons. 


Siemens & Halske High Speed 10,000 -volt Three-Phase Locomotive. 

It will be convenient at this point to digress from the question of geared versus 
gearless motors in order to describe another notable instance of an extra-high voltage 
locomotive. In order to operate the driving motors direct from the extra-high voltage 

354 










LOCOMOTIVES AND MOTOR CARRIAGES 



trolley line and to thus save the weight and expense of step-down transformers, it 
becomes inexpedient to locate the motors under the trucks of motor cars. It is 
distinctly advantageous in such cases to 
mount the motors on a locomotive and 
to keep all electric circuits away from 
the remainder of the train. In Figs. 

323 and 324 is illustrated a Siemens 
& Halske high speed locomotive equipped 
with four 250 li.-p. three-phase induction 
motors wound direct for 10,000 volts. 

While the drawings show four motors, 
two on each truck, only two motors 
appear to have been actually built, and 
the tests were run with but these 
two motors. 

The locomotive, which, with its 
equipment of two motors, weighs 40 
metric tons, has hauled a carriage of 
31 tons weight on the level at a speed 
of 65 miles per hour. Winding the 
motors direct for 10,000 volts, while it 
makes the motors large and heavy for 
their output, nevertheless considerably 
reduces the weight of the electrical equip¬ 
ment below that of an equipment with 
step-down transformers and low-voltage 
motors. 

The locomotive is equipped with 

two 10,000-volt, three-phase, six-pole induction motors. For a line periodicity of 
45 cycles per second, the corresponding synchronous speed of the motors is 900 
revolutions per minute. Other data are given below :— 


Fig. 322. 


Oerlikon Ovekhead High 
Tension Switch. 


Driving wheel diameter = 49 ins. 
Number of teeth in gear = 147. 

,, „ ,, „ pinion = 69. 

Gear ratio — 243 : 1. 


I rom this we find that the corresponding speed of the locomotive is 66 miles per 
hour. There is, of course, a slip varying with the load. In the motor in question, 
this involves a loss of speed of 11 per cent, when the output per motor is at the 
maximum 45-cycle 10,000-volt value of 400 li.-p. The predetermined characteristic 
curves of the motor corresponding to 10,000 terminal volts and a periodicity of 45 
cycles per second are given in Fig. 325. From these curves we find that the slip at 
350 li.-p. output per motor is 

900 — 845 

-- X 100 = 6*1 per cent. 

Drawings of the motor are given in Figs. 326, 327, and 328. A photograph of 
the wound stator is shown in Fig. 329, and a photograph of the motor assembled com¬ 
plete, with gears and gear cases, in Fig. 330. Gears are employed at both ends of each 

355 AA 2 






ELECTRIC RAILWAY ENGINEERING 


motor, owing to the large amount of power transmitted and to the high speed of the 
gear teeth. At a locomotive speed of 65 miles per hour, the speed at the pitch line of 
the gear teeth is 28 miles per hour. The diameter at the gear pitch line is 34*5 ins. 
This high speed requires special provision for lubrication. The means adopted 
consists in throwing the oil in several jets between the teeth at the entering side by 
the use of a low air pressure. 

The motor has a gap diameter of 26'8 ins., and a gross core length of 11'8 ins. 
The internal dimensions of the bearings are 12 ins. length by 4 ins. diameter. These 



Fig. 323. Siemens and Halske IIigii SrEED Locomotive, with 10,000-volt TniiEE-PnASE 

Motors. 


liberal proportions permit of employing a clearance at the air gap of only 0’07 ins. 
between rotor and stator. The bearings are of bronze, lined with white metal, and the 
lubrication is by means of oil and wicks. 

The Y-connected 10,000-volt winding is placed on the stator, as shown in Fig. 329, 
and consists of 36 form-wound coils of 67 turns per coil, assembled in 72 slots. There 
are thus 4 stator slots per pole per phase. The slot insulation consists of tubes of 
mica. Great reticence is for some reason observed with regard to the thickness of 
the slot insulation of these motors. This winding is stated to have withstood an 
insulation test of 22,000 volts from copper to iron. 

The rotor winding is a Y-connected wave winding consisting of 4 bars per slot in 
90 half-closed slots. There are thus 5 slots per pole per phase. Two of the terminals 

356 
























LOCOMOTIVES AND MOTOR CARRIAGES 


of the rotor winding are carried to the two collector rings shown in Fig. 326, and the 
remaining terminal is grounded to the core of the rotor. At starting, the pressure in 
the rotor winding is 700 volts between terminals. The rotor end connections are 
secured against centrifugal force by bronze caps, as shown in Fig. 326. 

Each motor weighs 4'1 metric tons. 

Fig. 331 gives a diagram of the electrical connections which were employed. At 
starting, and for speed regulation, rheostats are employed in series with the rotor 
windings. These rheostats are of the metallic type, and are subdivided into 24 steps. 

Exclusive of electrical equipment, the weight of the locomotive is 24 metric tons. 




Fig. 324. Siemens and Halske High Speed Locomotive, with 10,000-volt Three-Phase Motors. 

The total weight of the electrical equipment amounts to 16 metric tons. This gives a 
total weight of 40 metric tons for the locomotive equipped with two motors and 
accessories. Had it been equipped with its full complement of four 4‘1-ton motors 
instead of with only two such motors, the weight, with a reasonable allowance for 
increased weight of auxiliary electrical gear, would have been increased to about 
58 tons, or say 

Non-electrical equipment = 24 metric tons. 

Electrical ,, =28 ,, ,, 

The weight of the electrical equipment would thus have constituted some 54 per cent, 
of the total weight of the locomotive. 

The published reports of the tests on this locomotive are disappointingly vague. 

357 













































































































































































































































































ELECTRIC RAILWAY ENGINEERING 


They consist in stating that from June 17th to 26th, 1902, the voltage and periodicity 
were increased in successive tests, beginning with some 25 cycles and 6,000 volts, and 



Fig. 325. Characteristic Curves of 10,000-yolt Motors of the 
Siemens and IIalske Locomotive. 



runs were made at speeds of from 34 to 62 miles per hour. The last test was made 

June 26th, 1902, with 11,000 volts 
and a periodicity of 42‘5 cycles per 
second, when a railway carriage of 
31 tons weight was hauled. A 
maximum speed of 65 miles per 
hour was attained. It is stated 
that it was found that the gearing 
still ran fairly quietly, and that 
the motors operated fairly satis¬ 
factorily. It is stated that the 
locomotive and trailer both ran 
smoothly. The energy consump¬ 
tion was about 260 kilowatts. 
This corresponds to an output 
of about 280 h.-p. at the rims 
of the driving wheels. The loco¬ 
motive was found to be able to 
start from rest when hauling a 
load of some 90 tons, making, with its own weight, a train weight of 130 tons. 


Fig. 326. 


Siemens and IIalske 10,000-volt 
Three-Phase Motor. 


358 

























































































































































































































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 


The chief object of the tests was to demonstrate the practicability of employing 
polyphase motors wound directly for 10,000-volts pressure. It is, however, highly 



Fig. 327. Siemens and Halske 10,000-voet Three-Phase Motor. 


improbable that the use of 10,000-volt trolley lines will become necessary even in 
extensive railway projects. The heaviest work, can be very satisfactorily and 
economically carried out with from 3,000 to 6,000 volts at the trolley. Nor is it at 



\ 


X 


Fig. 328. Siemens and IIalske 10,000-volt Three-Phase Motor 

359 




























































































































ELECTRIC RAILWAY ENGINEERING 




Fig. 329. Stator of 10,000-volt Siemens and 
Halske Three-Phase Motor. 


all improbable that high trolley voltage will be combined with the use of continuous 

current motors. The practicability of 
such a plan has been maintained by 
various authorities. In 1904, one of the 
writers worked out such a scheme in 
order to make a comparison with a high 
voltage single-phase scheme. 1 The result 
was distinctly in favour of the high 
voltage continuous-current system. 

At that time the proposition met 
with no encouragement. High voltage 
continuous current for traction is, how¬ 
ever, now advocated by F. J. Sprague, 2 
who has expressed himself as follows :— 
“ On the general subject of alter¬ 
nating current and continuous-current 
operation, I beg to add a word. Affecting, 
as it vitally does, conductor capacity and 
sub-station distances, it is unfortunate 
that Mr. Scott should make a statement 
to the effect that 500 volts had become 
the standard, and, by inference, must necessarily be the limit for continuous-current 
operation, for although the New York Central’s rail supply will be at 650 volts, its 
continuous-current motors are guaranteed for 750, the Berlin Elevated and the 
Zweisimmen-Montreux roads are 
built for 800 to 850 ; reliable com¬ 
panies in Europe are supplying 
continuous-current motors wound 
for 1,000 volts, and it may be 
safely assumed that, in spite of 
apparent difficulties, turbine opera¬ 
tion of comparatively high voltage 
continuous-current dynamos is 
not an impossibility.” 

Two months later in a letter 
to the Street Railway Journal, 3 
Sprague again takes this matter 
up, and concludes his communi¬ 
cation as follows :— 

“ To that end I beg, therefore, 
to announce that if in any case, after considering the various kinds of equipment 


Fig. 330. 


Siemens and Halske 10,000-volt 
Three-Phase Motor. 


1 “ The Continuous-current System and the Single-phase System for Traction,” H. M. Hobart, 
Electrical Review, Yol. LIV., pp. 693—695, April 29th, 1904, and pp. 765—767, May 6th, 1904. See 
also “ Interurban Electric Traction Systems: Alternating versus Direct Current,” 1 J . M. Lincoln, 
Electrical World and Engineer, Yol. XLII., pp. 951—955, December 12th, 1903 ; discussion re above 
articles, Electrical Review, Yol. LIV., pp. 1031—1033, June 24th, 1904. 

2 “An Unprecedented Railway Situation,” Street Railioay Journal, A T ol. XXVI., pp. 775, 776, 
October 21st, 1905. 

:i P. 1089, December 23rd, 1905. 

360 





LOCOMOTIVES AND MOTOR CARRIAGES 


possible, it should seem from an analysis of all elements entering into the problem 
that a comparatively high potential continuous-current equipment would produce the 



Fig. 331. Diagram of Electrical Connections of Siemens 
AND HaLSICE 10,000-VOLT THREE-PHASE LOCOMOTIVE. 


best net results, I am prepared to engineer and carry to a successful conclusion a 
continuous-current installation at a working pressure, even on a third rail, of not 
less than 1,500 volts, which is at least two and a-half times that ordinarily used. 







































































































ELECTRIC RAILWAY ENGINEERING 


“ I believe that it may be admitted that, although I have oftentimes taken a some¬ 
what radical and advanced position in electric railway matters, I have never made a public 
proposal which I have not been ready, when called upon, to carry out, and should 
conditions arise warranting an equipment such as is proposed. I propose to establish a 
new and necessary comparative standard in equipment possibilities : and I venture 
further to affirm that 1,500 volts is not the limit of practical continuous-current 
operation." 

In view of this, and of support from other quarters, it is evident that the subject 
of higher voltage for continuous-current traction will now be taken up with more 
enterprise than has heretofore been displayed by electrical manufacturers, and the 
advocates of single-phase traction will no longer be able to confine their comparisons 
to high tension alternating current voltages on the one hand and 500-volt continuous- 
current third rail voltages on the other. 


5. tt' II. and A.E.G. High Speed Zossen Motor Cars. 

In the principal tests carried out at Zossen in 1903, two motor cars were used. 
These two cars were built respectively by the firms of Siemens & Halske and the 



Allgemeine Elektricitats Gesellschaft. The former is illustrated in Figs. 332 and 
333. and the latter in Figs. 334 and 335. In each case the equipment consisted of 
four gearless three-phase motors of a normal rating of 250 h.-p. per motor, and a 
maximum output of 750 h.-p. per motor. These motors were supplied from the 
secondaries of step-down transformers carried on the car. The primary current during 

362 





































































































































Fig. 332. Siemens and Halske High Speed Zossen Motor Car. 





























































































































































































































































































































































































































































































































































































































































































































































































































































































































’ 




































































LOCOMOTIVES AND MOTOR CARRIAGES 

the extra high speed tests was of a periodicity of 50 cycles per second at a pressure of 
10,000 volts. The S. & H. car had a complete weight of 77 metric tons, and 



/ 



i 



■ . 4 • 











•i-J 











I w 

\ 


■ 1 








employed a secondary pressure of 1,150 volts at the slip rings of the rotors which 
carried the motor’s primary-winding. The A.E.G. car weighed 90 metric tons, and 

3 ° 3 


Fig. 335 . Allgemeine Elektricitats-Gesellschaft High Speed Motor Oar used in Berlin Zossen Trials. 


































ELECTRIC RAILWAY ENGINEERING 


employed a secondary pressure of 435 volts at the terminals of the motor’s 
primary windings, which, in their design, were located on the stator. The 
S. & H. motors weighed 3'2 metric tons each, and the A.E.G. motors weighed 
4 - l metric tons each. The driving wheels of both cars were of 49'2 ins. (1,250 mm.) 
diameter. 

Considerable confusion exists as regards the weight of these cars. As 
originally constructed the Siemens and Halske car weighed some 77 tons, to 
judge from statements appended to a number of the test curves. To the A.E.G. 
car a weight of some 90 tons is ascribed in most instances. The tests extended over 
several years (1901 to 1903), and in consequence of structural modifications made 



4’ig. 330. S. & H. Motor for High Steed Zossex Motor Car. 


during this period, the weights of both cars are generally quoted as some 93 tons 
during the latest tests. This increased weight may, however, be partly ascribed to 
the weight of the personal and to the artificial load, these factors being different on 
different occasions. 

The S. & H. motors were mounted rigidly upon the driving axles, as shown in 
Eig. 336, while the A.E.G. motors were mounted on a hollow shaft and were spring 
supported from the driving wheels, as may be seen from the drawing in Fig. 337. 
Eig. 338 is a photograph of the spring supporting gear. 

Fig. 339 shows a photograph of the S. & H. rotor rigidly mounted on the shaft, 
and carrying the primary winding, and Fig. 340 shows a photograph of tbe A.E.G. 
rotor mounted on a hollow shaft and carrying the secondary winding. Eig. 341 shows 

364 



































































































































































































































































Fig. 338. Spring Supporting Gear for A.E.G. Motor. 



Fig. 339. Botor of Motor of S. & IT. Zossen Motor Car. 

365 


























































































































































































































































































































































ELECTRIC RAILWAY ENGINEERING 



Fig. 340. Eotor of Motor of A.E.G. Zossen 
Motor Car. 



Fig. 341. Kotor of Motor of A.E.G. Zossen Car in Place ox Axle. 



Fig. 342. Stator Core and Secondary Winding 
of Motor of S. & H. Zossen Motor Car. 
366 











LOCOMOTIVES AND MOTOR CARRIAGES 

a photograph of the latter rotor in place on the axle. Here again the method of 
spring support from the driving wheels may be seen. A photograph of the S. & H. 



Fig. 343. Assembled Motor of A.E.Gr. High Speed Zossen Motor Car. 


stator core and secondary winding is shown in Fig. 342. An assembled A.E.G. motor 
is show T n in the photograph in Fig. 343. 


ROLLING STOCK FOR MONO-RAIL TRACTION SYSTEMS. 

Ihe writers are of opinion that, so far as there is any future for mono-rail traction, 
somewhat better prospect of success rests with systems designed for underslung 
rolling stock. The Langen mono-rail system falls under this heading, and has already 
undergone a ceitain amount of practical development. In the space at our disposal 
it will l>e necessary to forego any complete description of this very interesting system. 



367 






























































































ELECTRIC RAILWAY ENGINEERING 


The chief advantage of the system consists in the possibility of traversing fairly 
sharp curves at high speed. The cars take the due inclination automatically in virtue 



p o uono?s 


Fig. 346. A Terminal Station or a Langen Mono-rail System. 






























































































































































































































































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 

of the centrifugal force. As the passengers are subject to the same force, they do not 
experience any disturbance. Indeed, it is claimed that they are not able to ascertain 



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whether the car is running on a curve or on a straight line unless they look out 


through the windows. 

E.R.E. 


B B 


369 










































































































































































































































































































































































































ELECTRIC RAILWAY ENGINEERING 

Fig. 344 shows drawings of the suspension of a carriage. The suspension is 
designed to prevent the carriage from leaving the rail under any circumstance. 



Fig. 345 gives the transverse and longitudinal sections of the carriages working at 
Elberfeld, and Fig. 346 shows one of the terminal stations. 

The principal data of these carriages are given in Table CYI. 

370 






































































LOCOMOTIVES AND MOTOR CARRIAGES 


Table CVI. 


Principal Data of a Carriage of 

Length between buffers . 

Width . 

Distance between the axles of the bogies 
Distance between the wheels of a bogie . 
Weight of a completely equipped car with all s 
Seating capacity .... 


the Langen Mono-rail System. 



. 39 

ft. 5 in. 

• 

. 7 

ft. 4 in. 

• 

. 22 

ft. 6 in. 

. 

. 3 

ft. 9 in. 

occupied. 

. 16 

tons 

• 

. 48 

passengers 



37i 


B B 2 




























































ELECTRIC RAILWAY ENGINEERING 


The carriages at Elberfeld are each equipped with two continuous-current 600-volt 
motors with a capacity of 35 h.-p. each. It is, however, only during acceleration that 
the motors are required to develop their rated load; at an average speed of 24 miles 
per hour the required power amounts to 23 h.-p. for each motor. 

The cars which were proposed for a projected railway for Berlin, as shown in 
Fig. 347, were designed for a capacity of 85 passengers each, and for a maximum 
speed of 34 miles per hour. For this project, the schedule speed works out at about 
18 5 miles per hour, and the average distance between stops is about half a mile. The 
loaded weight per car was estimated as 24 tons, and each was to be equipped with two 
motors of a maximum capacity of 100 h.-p. per motor. 

The rails are carried by a framework resting on iron supports of suitable form, 
which is, of course, varied in accordance with the construction of the line, as regards 
crossing over existing railways, tramways or rivers or public roads, or whether it must 
pass into a brick tunnel or an iron tube. 

The framework of the railway is so constructed as to involve a minimum of 
obstruction of light for the streets. The cars operate very smoothly and quietly. 

Fig. 348 and Fig. 349 show the sections of the railway as projected to pass over a 
river and over a street. Both forms were employed on the Barmen-Elberfeld- 
Yohwinkel Railway, and have stood the test of practical use very satisfactorily. The 
projected railway for Berlin was to be made as far as practicable on the lines of a quite 
different design, as shown in Fig. 350. On this plan, two beams with a sway-bracing 
between them are substituted for the framework. 

The station platforms are usually only about 16 feet above ground level, and lifts 
are therefore not necessary. 

It is stated that on curves of not less than 250 feet radius, the resistance does not 
exceed that on straight lines, and that as a consequence the power required for 
maintaining a given schedule speed is considerably lower than on other railways. It 
is also stated that sharp curves may be traversed at a speed more than twice as high 
as with standard railways. 


A STUDY OF THE RELATIVE WEIGHTS AND COSTS OF GEARLESS 

AND GEARED EQUIPMENTS. 

The question of gearless versus geared motors involves a consideration of the 
relative weights and costs of the two equipments, aside from the weight and cost of the 
remainder of the locomotives. It also involves questions of design, diameter of driving 
wheels, etc., owing to the limitations of space available for the motors. 1 In fact, the 
choice of ratio of gearing is restricted to fairly narrow limits by these and other 
considerations which we propose to now set forth. 

Let us first study the relation of the weight of an electric railway motor to its 
rated speed and rated capacity. In an article entitled “ Heavy Electric Railroading ” 


1 For passenger railway carriages with motors on trucks, the diameter of the driving wheel is 
necessarily small (generally 33 ins.) ; but in the case of locomotives the diameter of the driving wheel 
should be determined upon with especial care, and one of the determining factors should be the 
limitations of space available for the motors. 


372 


LOCOMOTIVES AND MOTOR CARRIAGES 

on p. 860 of the Electrical World and Engineer for November 18th, 1905, Yalatin 
las given inteiesting data, from which, together with data from other sources, we have 
deduced the following results. 

The “ weight coefficient ” may be defined as follows 

Weight coefficient = Bated horse-power (1-hour 75 degrees Cent, basis) _ 

Weight in metric tons (exclusive of gearing) X speed in r.p.m. 



Fig. 351. Curves showing Variation of Weight Coefficient of Railway Motors, 

with Speed in Revolutions per Minute. 


Then for continuous-current railway motors of from 500 to 1,000 volts we have the 
rough representative values for the weight co-efficient shown in Table CVII. 


373 





































































































































Tot&! weight of Motor m Metric Tons 


ELECTRIC RAILWAY ENGINEERING 

Table CVIL 


Weight Coefficients of Continuous Current Railway Motors. 


Rated Output in 
Horse-power. 

Weight Coefficien 

Horse-power 


Rated Speeds:— 

v Metric Tons x R.P.M. ““ " . . 

r 

200 R.P.M. 

400 R.P.M.i 

600 R.P.M. 

SOO R.P.M. 

75 

0-16 

o-ll 

0-080 

0-065 

150 

0-21 

0-15 

0*11 

0-085 

300 

0-27 

0-20 

0-15 

0-12 


The values have been plotted in Fig. 351, which gives curves showing the relation 
between speed and weight coefficient for motors rated at 75, 150, and 300 h.-p. 

This gives us for the total weight of motors, exclusive of gearing, the values shown 
in Table CVIII. 


Table CVIII. 


Total Weights of Continuous Current Railway Motors, exclusive of Gearing. 


Rated Output in 
Horse-power. 

Total Weight of Motor (exclusive of Gearing) in Metric Tons for 
Following Rated Speeds :— 

L 

200 R.P.M. 

400 R.P.M. 

600 R.P.M. 

800 R.P.M. 

75 

2-3 

1-71 

1'56 

1-44 

150 

3-6 

2-5 

2-3 

2-2 

300 

5-6 

3-8 

3-3 

3-1 



0 SO WO ISO ZOO ZSO 500 SSO 400 4S0 SOO S50 foOO bSO JOO 7SO 800 


Speed of Motor m Revs per Min 

Fig. 352. CURVES SHOWING VARIATION OF THE TOTAL WEIGHT OF RAILWAY MOTORS, WITH 

Speed and Revolutions per Minute. 

374 





























































































Polyphase M otors. Single-phase Com. Motors. Con.-current Motors. 


LOCOMOTIVES AND MOTOR CARRIAGES 

These values have been plotted in Fig. 852, giving curves showing the relation 
between speed and weight for motors of 75, 150, and 800 h.-p. 

Single-phase commutator railway motors will weigh considerably more than the 
above values, and three-phase railway motors may weigh considerably less. 

\ alatin s data constitute a valuable source of reference, and are therefore 
reproduced in Table CIX., by permission : 


Table CIX. 

I alatin's Data for Railway Motors. 


r i 


5 

6 

"I 7 
8 


10 

11 

U2 

r is 

14 

15 

16 

17 

18 


19 

20 

121 
f 22 


Zo 

24 

25 

26 

27 

28 
29 


30 

31 

32 

33 

34 

35 

36 
137 


1 





73 



Weight in 
Metric Tons 


3 ^ 





. 



be 


• 73 








>> . 

3 




- £ 

ace 

a 














Name of Manufac¬ 
turer and Type of 

Name of the Line 
where Motor was 

6 


09 

be 

ct 

.5 o 

o 


6 

& 

g 


be 

03 1—1 

tl o 

«r 

tT > 

O fc 
H .g 

5 

Motor. 

used. 

rr. 

t—i 

O 

a 

03 

go 

'o 

’o ^ 

o 

o 

+3 

i-i 

eg 

03 

o 

^ t-J 
2 cs 

— 03 

oO 

—. 03 

go 

li £ 

I 03 Sh 
O - 
O O 

<D a 

gc 

03 

o 

o 

r Jl 





03 



►5 

W 


. 03 






P-l 





-s'- 

& K 


U. Elek. Gesell.— 

— 

50 

5S0 

_ 


Geared 



1-35 

0-064 


“ G.E. 57 ” 












Westinghouse “56 ” 

— 

55 

475 

_ 

_ 

Geared 

_ 

1-360 

1-22 

0-095 


Siemens & Halske, 

Berlin Elev. and Subway 

60 

800 

750 

_ 

Geared 

1:4 

1-575 

1-40 

0-054 


D. 17/30 










Westinghouse “ 56 ’ 

— 

75 

490 

_ 

_ 

Geared 

_ 

1-940 

1-80 

0-0S5 


Siemens & Halske, 

— 

85 

720 

750 

_ 

Geared 

_ 

1-750 

1-55 

o-o 

76 


19/30 









General Electric Co 

C.L. Ry. motor car, 

100 

475 

500 

_ 

Geared 

1:27 

_ 

1-82 

0-116 



first type 












Westinghouse “ 56 ’ 

— 

150 

550 

— 

— 

Geared 

_ 

2-400 

2-25 

0-121 


Oerlikon. 

Freiburg-Musten Line 

150 

400 

750 

— 

Geared 

1:4 

3-050 

2-70 

0-139 



motor car 












Gen. Elec. Co., 

C.L. Ry., geared loco. . 

150 

500 

500 

— 

Geared 

1:3-3 

_ 

2-46 

0-122 


“G.E. 55A ” 












Gen. Elec. Co., 

C.L. Ry., gearless loco. 

170 

165 

500 

— 

Direct 

_ 

— 

5-42 

0-190 


“ G.E. 56 ” 













Siemens & Halske, 

— 

210 

520 

— 

— 

Direct 

_ 

— 

4-10 

0-098 


D. 25/50 













General Electric Co 

N.Y.C.and H.R.R. loco. 

550 

300 

600 

— 

Direct 

— 

— 

5-0 

0-367 


Oerlikon 

Experimental motor 

35 

1000 

200 

25 

Geared 

— 

— 

1-00 

0 035 

Street Ry. Jour., 

A.E.G. Union, W.E. 

Stubaithal motor car . 

40 

800 

550 

40 

Geared 

1:5-07 

— 

1-39 

0-036 

1905, IV., 8. 
Elek. Bah. u. Bet., 

31 

Gen. Elec. Co., 

Schenectady Ballston 

50 


200 

25 

Geared 

1:3-74 





1905, p. 297. 

G.E.A. 604 

Line 












Gen. Elec. Co., 

Bloomington, Pontiac, 
and Joliet Line 

75 

700 

200 

25 

Geared 

1:4 3 

— 

1-9 

0-056 

Street Ry. Jour., 
1905. 

G.E. A. 605 











Siemens-Schuckert 

Murliau-Oberammergau 

100 

530 

270 

16 

Geared 

1:5 


— 



Elek. Bah. u.Bet., 

A. E.G. Union 

Spindlersfeld Railway . 

100-120 

800 

6000 

25 

Geared 

— 

2-360 

2T0 

0-059- 

0-071 

1905, p. 388. 

Westinghouse 

Swedish Govt. loco. 

150 

1270 

200 

25 

Geared 

1:3-88 

— 

2-50 

0-047 


Oerlikon. 

Proposed loco. 

200 

650-1000 

— 

15 

Geared 

— 

— 

3 00 

0-103- 

Street Ry. Jour., 











0-066 

1905, IV., 8. 

Westinghouse 

Experimental loco. 

225 

300 

140-325 

— 

Geared 

1:5-27 

— 

— 

— 


Street Ry. Jour. 

Brown-Boveri 

Burgdorf-Thun mot. car 

60 

600 

750 

40 

Geared 

1:3 

— 

1-50 

0-066 

Siegfried Herzog 


Burgdorf-Thun loco. 



750 








die Elek. Anla- 
gen der Schweiz. 

Brown-Boveri 

150 

300 

40 

Geared 

1:1-88 

— 

4-00 

0-125 

Brown-Boveri 

Jungfrau loco. 

120 

750 

500 

38 

Geared 

— 

— 

2-10 

0-076 


Siemens & Halske . 

Marienfeld - Zossen J 

250 n. 

l 900 

1150- 

45-50 

Direct 



3-20 

o-oso 



High Speed Railway 1 

750 m. 

1850 



0-240 


A.E.G. . 

Marienfeld - Zossen ( 
High Speed Railway 1 

250 n. 
750 m. 

| 960 

435 

50 

Direct 

— 

— 

4-08 

0-064 

0-192 


Ganz & Co. 

Wollersdorfer loco. 

75 

600 

3000 

42 

Geared 

1:6 

1-440 

1-07 

0-118 


Ganz & Co. 

Canada motor car 

120 

750 

1100 

25 

Geared 

1:3-27 

— 

1-75 

0 091 


Ganz & Co. 

Port Madoc loco. 

180 

750 

600 

50 

Geared 

1:3 

— 

1-61 

0-149 








and driv. 
coup, rod 







Ganz & Co. 

Valtellina old loco. 

225 

128 

3000 

15 

Direct 

— 

— 

4-90 

0-358 


Ganz & Co. 

Valtellina motor car 

250 

300 

3000 

15 

Direct 

— 

— 

3-SO 

0-219 


Ganz & Co. 

Proposed loco. Inter- 

400 

168 

2000 

14 

Coup, rod 

— 

— 

6-95 

0-343 



urban 












Ganz & Co. 

Proposed motor car 

350 

990 

3000 

30 

Geared 

1:3 1 

2-S00 

2-55 

0-152 



Interurban 












Ganz & Co. 

Proposed loco. 

600 

225 

3000 

15 

Direct-con. 

— 

— 

6-70 

0 39S 


Ganz & Co. 

New Valtellina loco. 

000 

225 

3000 

15 

Coup, rod 

— 

— 

8-15 

0-327 



without cascade motor 












Ganz & Co. 

New Valtellina loco. 

450 

112-5 

3000 

15 

Coup, rod 

— 

— 

12 -40 

0-322 



with cascade motor 












Ganz <fc Co. 

Italian State Railways. 

1500 

225 

— 

— 

— 

— 


13-10 

0-51 




375 





















































































ELECTRIC RAILWAY ENGINEERING 


One may, for rough preliminary estimates, take the weight, including gear and 
gear case, at a 15 per cent, higher value than the weights in Table CVIII., although the 
precise percentage is, of course, a function of the power to be transmitted, the ratio of 
gearing, and the design of the gear and gear case. 

Taking for the present, tbe weight without gear and gear case and confining our 
attention to continuous-current railway motors, we may transfer our ideas from weight 



Fig. 353. Curve Showing relation of Weight of Motor in Metric Tons 
to D 2 a (j of Armature for Continuous Current Eailway Motors. 


to volume by a consideration of the* curve in Fig. 353. This curve conforms 
sufficiently to good modern practice to serve our purpose of arriving at the approximate 
limiting quantities. 

DS = diameter of armature at air gap in centimetres. 

Y gross length of armature core between end flanges in centimetres. 

By means of this curve we may obtain the values set forth in Table CX. 


Table CX. 


I alues of D 2 \g for Continuous-current Railway Motors. 


Rated Output in 
Horse-power. 

DUg of Continuous-current Railway Motors for Following Rated 
Speeds in R.P.M. at Rated Loads. 

DS and \g are expressed in Centimetres. 

-- 

200 R.P.M. 

400 R.P.M. 

600 R.P.M. 

800 R.P.M. 

75 

150 

300 

91,000 

145,000 

235,000 

61,000 

100,000 

158,000 

51,000 

90,000 

135,000 

50,000 

85,000 

123,000 


The armature diameter for single reduction geared motors will generally be equal 
to from 35 per cent, to 65 per cent, of the diameter of the driving wheels. We 
may take 50 per cent, as a mean value for the purpose of arriving at general 

376 





























































LOCOMOTIVES AND MOTOR CARRIAGES 

conclusions. This value will also be fairly representative for gearless motors. For given 
diameters of driving wheels, and for motors of given weight, we can therefore deduce 



Fig . 354 . Curves showing Yaeues of Gross Core Length of 
Armature for various Weights of Motors and Diameters of 
Driving Wheels. (See Table CXI.) 


the value of kg, the gross core length. The gross core length is shown in centimetres in 
Table CXI., and in the curves of Fig. 354, it is plotted in inches. 


Table CXI. 

Gross Length of Core in Centimetres (a g) of Motors of various Weights, for Driving 
Wheels of various Diameters, taking D = 05 X Diameter of Driving Wheel. 


. C 

o H 


1-44 

1-56 

1 - 71 

2 - 2 

2-3 

2 - 5 

3 - 1 

3-3 
3-6 
3-8 
5-6 


D^Ag. 


Diameter of Driving Wheel in Inches. 



30. 

32. 

34. 

36. 

38. 

40. 

42. 

44. 

46. 

48. 

1 

50. 

55. 

60. 

70. 

80. 

50,000 

34-5 

30-3 

26-9 

24 

21 5 

19-4 

17-6 

16-0 

14-6 

13-5 

12-4 

10-2 

8-61 

6-32 

4-85 

50,600 

34-9 

30-7 

27-2 

24-2 

21-7 

19-6 

17-8 

16-2 

14-8 

13*6 

12-6 

10-3 

8-7 

6-40 

4-91 

60,300 

41-6 

36-6 

32-5 

28-9 

25-9 

23-4 

21-2 

19-3 

17-7 

16-3 

14-9 

12-3 

10-4 

7-63 

5-85 

85,500 

58-6 

51-5 

45-7 

40-7 

36-5 

33-0 

29-9 

27-2 

24-9 

22-9 

21-1 

17-4 

14-6 

10-7 

8-25 

90,300 

62.3 

54-7 

48-6 

43-3 

38.8 

35-0 

31-8 

28-9 

26-4 

24 3 

22-4 

18-4 

15-5 

11-4 

8-75 

100,000 


60-6 

53-8 

48-0 

43-0 

38'7 

35-2 

32-0 

29-3 

26-9 

24-8 

20-4 

17-2 

12-6 

9-7 

122,500 




587 

52-6 

47-5 

43-1 

39-2 

35-8 

33-0 

30-4 

25-0 

21-1 

15-5 

11-9 

135,000 





58-0 

52-3 

47-5 

43-2 

39-5 

36-4 

33-4 

27-6 

23-2 

17-1 

13-1 

145,000 





63-4 

56-1 

51-0 

46-5 

42-5 

39-1 

36-0 

29-6 

24-9 

18-4 

14-1 

157,000 






60-8 

55-3 

50-3 

46-0 

42-3 

38-9 

32-1 

27 0 

19 9 

15-2 

235,000 




1 

I 

| 




63'3 

58-2 

43-0 

40-5 

29-7 

22-8 




o 


Values below the heavy black lines refer to gearless motors only. 


377 
































































































































































ELECTRIC RAILWAY ENGINEERING 


As a very rough guide, but as one which will enable us to arrive at certain 
approximate conceptions, let us take the length of the motor over its frame as equal, for 
gearless motors, to twice the gross core length, and as equal to three times the gross 
core length for geared motors, as the latter require independent bearings. These 
figures have been chosen after examining the dimensions of a number of traction 
motors. For gearless motors the ratio is generally near 2, and for geared motors it 
varies from 8 to 4’5. The larger figures are, however, for standard motors of several 
years ago, the most modern designs making the length over frame more nearly 3 
for geared motors. Hence we have chosen the latter figure as a basis for comparison. 
The length over frame does not include the gearing, which latter generally occupies 
some 5 to 8 ins. axially. 

Confining our attention to the standard gauge of 4 ft. 8^ ins., it will not be 
practicable to allow more than 50 ins. of overall width of motor frame for gearless 
motors, or more than, say, 43 ins. for geared motors. In the latter case, the remaining 
space is occupied by the speed reduction gearing. The maximum gross core length 

50 

of a gearless motor which can be got in, is thus — = 25 ins., and for geared 

A 

43 

motors — = 14 ins. The heavy line in Table CXI. indicates the limit for geared 

O 

motors, all core lengths above this line being less than 14 ins., and no core 
length is included which is greater than 25 ins., the limit for gearless motors. 
The precise value of all such limitations is a matter of detail designing, whereas 
our present object is to arrive at a broad view of the general nature of the 
limitations. 

We are now able to construct Table CXII. and Fig. 355, which show us for any 
given weight of gearless motor the minimum practicable diameter of driving wheel, 
and, in a similar way, Table CXIII. and Fig. 356 for geared motors. 


Table CXII. 


Overall Length oj Frame, in Inches, of Gearless Motors of various Weights for 

Driving Wheels of various Diameters. 


Tc-~ = 

^ o o 

m\g. 






Diameter of Drivin 

g Wheel in Inches. 





s 


30. 

32. 

34. 

36. 

38. 

40. 

42. 

44. 

46. 

48. 

50. 

55. 

60. 

70. 

so . 

1-44 

50,000 

27-2 

23-9 

21-2 

18-9 

16-9 

15-3 

13-7 

12-6 

11-5 

10-6 

9-76 

8-03 

6-78 

4-98 

3-82 

1*56 

50.600 

27-5 

24-2 

21-4 

191 

17-1 

15-4 

14-0 

12-7 

11-6 

10-7 

9-83 

8-11 

6-85 

5-04 

3-87 

1-71 

60.300 

32-8 

28-8 

25-6 

23-7 

20-4 

18-4 

16-7 

15-2 

13-9 

12-8 

11-7 

9-70 

8-20 

6-01 

4-60 

2-2 

85,500 

46-1 

40-5 

36-0 

32 1 

28-7 

26-0 

23-5 

21-4 

19-6 

18-0 

16-6 

13-8 

11-5 

8-42 

6-50 

2-3 

90,300 

49-0 

43-1 

38-3 

35-7 

30-6 

27-5 

25-0 

22-7 

20-8 

19-1 

17-6 

14-5 

12*2 

8-97 

6-90 

2-5 

100,000 


47-7 

42-4 

37-8 

33-9 

30-5 

27-7 

25-2 

23-1 

21-2 

19-5 

16-1 

13-5 

9-9 

7-64 

3-1 

122,500 




46-2 

41-4 

37-4 

34-0 

30-8 

28-2 

26-0 

23-9 

19-7 

16-6 

12-2 

9-36 

3-3 

135,000 





45-6 

41-2 

37-4 

34-0 

31-1 

28-6 

26-3 

21-7 

18-3 

13-5 

10-3 

3-6 

145,000 





49-8 

44-1 

401 

36-6 

33-4 

30-8 

28-3 

23-3 

19-6 

14-5 

11-1 

3-8 

157,000 






47-9 

43-6 

39-6 

36’2 

33-3 

30-6 

25-3 

21-3 

15-7 

12-0 

5-6 

235,000 










49-8 

45-8 

33-9 

31-9 

23-4 

18-0 


37§ 


Overall Length of Frame in Inches. 









































LOCOMOTIVES AND MOTOR CARRIAGES 

Table CXIII. 

Overall Length of Frame, in Inches, of Geared Motors of various Weights for 

Driving Wheels of various Diameters. 


Diameter of Driving Wheel in Inches. 


Total Wei 
of Motor 
Metric Ti 

D -%. 

. . 1 ^ m iiiwico, 

30. 

32. 

34. 

36. 

38. 

40. 

42. 

44. 

46. 

48. 

50. 

55. 

60. 

70. 

so . 

1-44 

50,000 

40-7 

35-8 

31-8 

28‘3 

25-4 

22-9 

20-8 

18-9 

17-3 

15-7 

14-6 

12-1 

10-2 

7-47 

5-73 

1-56 

50,600 

41-2 

36-2 

32-2 

28‘6 

25‘6 

23-1 

21-0 

19-1 

17-5 

16-1 

14-9 

12-2 

10-3 

7-56 

5-8 

1-71 

60,300 


43-2 

38-4 

33-0 

30-6 

27-6 

25 T 

22-8 

20-9 

19-3 

17-6 

14-5 

12-3 

9-02 

6-91 

2‘2 

85,000 





43 T 

39-0 

Q ft . O 

dO d 

32-1 

29-4 

27 T 

24-9 

20-6 

17-2 

12-6 

9-75 

2-3 

90,300 






41-3 

37-6 

34-2 

31-2 

28-7 

26-5 

21-7 

18-3 

13-5 

10-3 

2-5 

100,000 







41-6 

37-8 

34-6 

31-8 

29-3 

24 T 

20-3 

14-9 

11-4 

3-1 

122,500 









42-3 

39-0 

35-9 

29-5 

24-9 

18-3 

14-1 

3-3 

135,000 










43-0 

39-5 

32-6 

27-4 

22-0 

15-5 

3-6 

145,000 











42'5 

35-0 

29-4 

21-7 

16-7 

3-8 

157,000 












38-0 

32-0 

23 5 

18-0 

5-6 

235,000 














35-1 

26-9 


As already suggested, these results are controlled by our fundamental assumptions, 
which can only be general. Cases will be found where greater weights of motor are 



Fig . 355 . Curves for Gearless Motors, showing Overall Length of 
Motor Frame for various Motor Weights and Diameters of 
Driving Wheels. (See Table CXII .) 


associated with given driving wheel diameters ; nevertheless it is instructive to examine 
the tendencies at work. The limitations here arrived at are of a general order, which 
will lead to a sound design without undue crowding of parts, and without resorting to 
unusual designs as regards form of motors or their location. 

The diagrams in Fig. 357 have been constructed from the diagrams in Figs. 355 
and 356, and show us, for motors of 75, 150, and 300 h.-p. respectively, the relation 
between the limiting lowest armature speed at rated output and the driving wheel 

379 


Overall Length ol Frame in Inches. 































































































ELECTRIC RAILWAY ENGINEERING 


diameters. The limiting lowest speed is determined reference to Fig. 352, which 
gives a connection between the weight and speed of the motor. From Figs. 355 and 
356 we can ascertain what is the weight of the heaviest motor that can be used with 
a given driving wheel, and then, referring to the curves of Fig. 352, we obtain the 
motor speed corresponding to this weight. In this way we have plotted the limiting 
lowest speed practicable, against the diameter of driving wheel for 75, 150, and 
300 h.-p. gearless motors in the upper horizontal set of curves in Fig. 357. For geared 
motors we assume that the gearing occupies 7 ins., or 15 per cent, of the length 
between wheels, the maximum available length for the motor frame being thus 43 ins. 



Fig . 356 . Curves for Geared Motors, showing Overall Length of 
Motor Frame for various Motor Weights and Diameters of 
Driving Wheels. (See Table CXIII.) 


Hence we have set this as the limiting motor frame length in Fig. 356, and have 
derived in a similar way to that just described for gearless motors, the lower horizontal 
set of curves in Fig. 357, showing the lowest speeds practicable with various driving 
wheel diameters for motors of 75, 150, and 300 h.-p. 

The limiting highest speed is partly a question of commutation and partly a 
question of mechanical design, in which a leading consideration is the design of the 
reduction gearing. The ordinary series-wound railway motor, when running at light 
loads, attains a speed of the order of twice its speed at its rated output. It would 
therefore appear reasonable to assign the following values as the highest limiting 
speeds at rated loads :— 

75 h.-p . 800 r . p . m . 

150 h.-p . 600 ,, 

300 h .- p . . . . . . . 400 „ 

We have now the highest limiting speed, and the lowest limiting speed as a 
function of the driving wheel diameter, for motors of 75, 100, and 300 h.-p. In 
Tables CXE ., CXV., and CXYI., we have set out the practicable motor speed in revolu¬ 
tions per minute necessary to give running speeds ranging upwards, from 15 miles 
per hour with driving wheels of diameters from 30 ins. upwards, these three tables 
relating respectively to 75, 150 and 300 h.-p. motors. 

380 











































LOCOMOTIVES AND MOTOR CARRIAGES 



3» i 




















































































































































































































































































































































































































Table CXIY. 

Speeds of 75-h.-p. Motor for various Locomotive Speeds in Miles per Hour and various Driving Wheel Diameters. 


ELECTRIC RAILWAY ENGINEERING 







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382 









































































LOCOMOTIVES AND MOTOR CARRIAGES 

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383 









































































ELECTRIC RAILWAY ENGINEERING 

Table CXVI. 

Speeds of 300 -h.-p. Motor for various Locomotive Speeds in Miles per Hour and 

various Driving Wheel Diameters. 


Ratio of Gearing. 


Diameter of 
Driving 
Wheel in 
Inches. 

1 :1. 

1 

2. 


1 :3. 

1 

4. 

1 

5. 

Speed in Miles per Hour. 

Speed in Miles per Hour. 

Speed in Miles 
per Hour. 

Speed in 
Miles 
per Hour. 

Speed in 
Miles 
per Hour. 


30. 

40. 

50. 

60. 

so. 

15. 

20. 

30. 

40. 

15. 

20. 

30. 

15. 

20. 

15. 

20. 

30 

















32 

















34 

















36 

















38 

















40 

















42 


320 

400 














44 


305 

382 














46 


292 

365 














48 

210 

280 

350 














50 

202 

268 

336 

402 







402 






55 

183 

244 

305 

366 




366 



366 


368 




60 

168 

224 

280 

336 



224 

336 


252 

336 


336 




70 

144 

192 

240 

288 

383 


192 

288 

384 

216 

288 


288 

384 

360 


80 

126 

168 

210 

252 

336 


168 

252 

336 

189 

252 

378 

252 

336 

315 



No speeds are included in these tables which fall below the lowest limiting speeds 
of Fig. 357, or above the highest limiting speeds given above. The results in 
Tables CXIV., CXY., and CXYI. have been plotted in Fig. 358, which gives a series of 
enclosed areas obtained by plotting the maximum and minimum practicable speeds of 
motor for each speed of train in miles per hour (corresponding to the various driving 
wheel diameters). These areas indicate the limits of motor speed and train speed for 
motors of 75, 150, and 300 rated h.-p. for various gear ratios. Thus, supposing the 
locomotive speed and its rated horse-power are given, we can determine the most desir¬ 
able motor speed and driving wheel diameter. It is now probable that the best point 
at which to work will be somewhere in the region of the centre of gravity of each 
of the areas in Fig. 358. Hence we have determined roughly the centre of each area, 
and in Table CXYII. we have brought together the particulars of the motors 
corresponding to each of these points. 

Table CXYII. shows the speed in miles per hour, the revolutions per minute of 
the motor, diameter of driving wheel, and weight per horse-power of output. The 
weight of motor and gearing has been included on the assumption that the gearing 
weighs an additional 15 per cent, of the motor weight. Taking the weight of the 
auxiliary equipment at 0'005 ton per horse-power, the total weight of motor, gearing, 
and equipment per horse-power, has been added. The figure of 0'005 ton per horse¬ 
power is based on the figures for four representative locomotives, particulars of which 
are given in Table CXYIII. The weight of the auxiliary equipment per horse-power 
comes out to a very uniform value in these cases, the average being 0'005 ton per 
horse-power. 


384 


Motor Speed in Revolutions per Minute. 























































Ordinates denote Speed of Motor in Revolutions per Minute 




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p ig . 338 . Limiting Valdes oe Motor Steed (e.f.m.) for different Train Steeds (Miles ter Hour) for Motors of 75, 150, and 300 h.t. 



































































































































































































































































































































































































































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385 


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E.R.E 
























































































ELECTRIC RAILWAY ENGINEERING 

Table CXYIII. 

Data for Weights of Locomotives and Motor Equipments. 




Weight in Metric Tons. 

Wei° 

dit in Metric Tons per H.-P. 

Railway on which Locomotive 
is used. 

Total 

H.-p.of 

Motors. 

Complete 

Loco¬ 

motive. 

Electrical 

Equip¬ 

ment, 

including 

Motors. 

Motors 

only. 

Electrical 

Equip¬ 

ment 

only. 

Complete 

Loco¬ 

motive. 

Electrical 

Equip¬ 

ment, 

including 

Motors. 

Motors 

only. 

Electrical 

Equip¬ 

ment 

only. 

Baltimore and Ohio, 
Geared 

800 

73 

20-3 

16-1 

42 

0 091 

0-0255 

0-0201 

0-00526 

Paris-Orleans, 

Geared 

1,000 

49 

21-3 

16-2 

5-0 

0-049 

0 0213 

0 0162 

0-00500 

New York Central, 
Gearless 

2,200 

85 

27-8 

17-1 

10-6 

0-0386 

0-0125 

0-0077 

0-00477 

Central London Railway, 
Gearless 

680 

44-3 

24*8 

21-8 

3 0 

0 0645 

0 0321 

00320 

0-00435 


The results in Table CXVII. have been plotted in Fig. 359. The curves in the left- 
hand column of this figure show the variation of weight of motor gearing and equip¬ 
ment, with the speed in miles per hour, for motors of 75, 150, and 300 li.-p. In the 
right-hand column of the same figure the curves show for any given speed in miles 
per hour the motor speed (revolutions per minute), the driving wheel diameter, and 
the gear ratio. 

The weight of the rheostats and control apparatus in general, is, of course, a 
function of the frequency and duration of rheostatic running. Hence for very severe 
service 0'005 tons per horse-power will not cover the weight of equipment other 
than motor weight, and this figure may approach 0'008 or even 0010 tons per horse¬ 
power. Of course, however, it will be independent of the ratio of gearing and the 
diameter of the driving wheels. 

A high voltage traction system is necessary before thoroughly rapid progress can 
be made in superseding steam by electricity on main line railways. Some progress 
has already been made along these lines, both with single-phase and polyphase 
systems. An as yet much-neglected system is that employing high voltage con¬ 
tinuous-current motors. Some years ago 1 one of the present writers put in a word for 
this system, and in a fairly careful comparison for a certain case, arrived at results 
which were much more satisfactory than those obtained by single-phase operation. 
But little interest could then be roused on the subject. Now, however, it is again 
attracting attention, and, in one form or another, will doubtless be actively followed, 
up. High tension continuous-current railway motors are already on the market, and 
it is the writers’ belief that half the sum spent in developing the single-phase 
commutator motor to its present condition (in which it still remains less efficient, more 
bulky, and less satisfactory in several respects than the 600-volt continuous-current 
motor) will result in the development of thoroughly satisfactory high tension con¬ 
tinuous-current motors. These motors will be as efficient and as light for a given 
temperature rating and a given speed, as the present standard 600-volt motors. The 
commutation will be better. As traction motors increased in size, they were designed 

1 “ The Continuous-current System and the Single-phase System for Traction,” H. M. Hobart, 
Electrical Review , London, Vol. LIV., p. 693, April 29th, and May 6th, 1904. 

386 




























LOCOMOTIVES AND MOTOR CARRIAGES 


successively with five, four, three, two, and finally one turn per segment. Beyond that 
point, the commutation difficulties with increasing capacity can only be met with 
reversing poles, or their equivalent. Going up to 1,500 volts and higher, it will again 
be practicable in motors of large capacity to improve the commutation in virtue of the 



Fig. 359. Curves showing Relation between Speed of Locomotive and Driving Wheel 

Diameter, Motor Speed, and Weight. 


decreased current, and when, in addition to this, reversing poles are employed (in the cases 
where they are suitable), there need be no apprehension that commutation will present 
any difficulties. Indeed, the commutator of a 1,500-volt continuous-current motor will 
be much shorter than that of a 600-volt continuous-current motor, since the current 
to be collected is so much less. The total brush surface will be correspondingly 

387 CC 2 












































































































































































ELECTRIC RAILWAY ENGINEERING 


reduced. Thus a greater space between wheels may be devoted to armature and 
winding, and motors of larger capacity will be practicable for a given driving wheel 
diameter and gear ratio. In other words, the limiting areas in Fig. 358 will become 
larger. The very slightly increased space necessary for high voltage slot insulation, 
will be an almost negligible factor as affecting the bulk of the motor for a given rated 
capacity when this rated capacity is a matter of 100 h.-p. and upwards. 1 

If, on the other hand, we turn our attention to the single-phase commutator motor, 
we find it in j)ossession of over twice as large a commutator (as this is for 250 volts) 
as its 600-volt continuous-current equivalent. This alone takes away valuable space 
between wheels, and leaves a less available width for the armature. As, however, the 
latter also is large for its rated output (for equal rated speeds), the areas corresponding 
to those in Fig. 358, are, for single-phase commutator motors, very restricted indeed. 
There will be a tendency to keep down the dimensions by employing a higher rated 
speed and ratio of gearing. This means, in motors of high rated capacity, serious 
losses in gearing and rapid deterioration of gearing. It is also unfavourable for 
commutator and brushes. 

There thus appears good reason to anticipate better results from high voltage 
continuous-current traction than from single-phase traction with commutator motors. 
For long distance service, however, both may in the course of development be sur¬ 
passed by the polyphase induction motor, which, when examined on the plan of the 
diagrams of Fig. 358, shows up very favourably in this class of service. For loco¬ 
motive service, sight must not be lost of the alternative single-phase system with a 
motor-generator on the locomotive, intermediate between the high tension line and the 
motors. Even in this case, fairly high tension continuous-current motors on the 
trucks may give the best results because of the more compact commutator and the 
more satisfactory commutation which will be obtained in large capacity motors, by an 
increase in the armature voltage. 

The lower saturation necessary in an alternating-current motor as compared with 
a continuous-current motor, the impracticability of employing the outer shell as 
active material in the magnetic circuit, the larger commutator and greater amount of 
brush gear, tend to make the single-phase motor very heavy for its dynamical 
capacity, compared with the continuous-current motor. Moreover, the former is so 
much lower in efficiency than the latter, and accordingly has to dissipate so much 
more heat, that the service capacity is low in comparison with the dynamical capacity. 
Any service, therefore, which makes the heating of the motors a limiting feature, 
requires a weight of single-phase motor equipment far in excess of that necessary on 
the continuous current system. 

The great disadvantage of the single-phase motor as regards weight, has been very 
clearly brought out by Carter in his reply to the discussion of his recent paper entitled 
“ Technical Considerations in Electric Railway Engineering ” (read before the British 
Institution of Electrical Engineers, January 25th, 1906). In the discussion on the 
paper, Dawson made the following statement:— 

“ The weight of a 150-h.-p. motor, rated on the American principle to which the 
author referred, is 2*7 tons, and the weight of a 115-h.-p. motor rated exactly on the 

1 For smaller capacities, 1,500-volt continuous-current armatures would, through the increased 
space required for slot insulation, be slightly larger for a given output and speed. In a general way, 
the most favourable voltage, from the standpoint of the design of the motor, increases as the rated 
output increases. 


3 88 


LOCOMOTIVES AND MOTOR CARRIAGES 

same basis is 2*4 tons. If we take the weights of two motor trucks, one set equipped 
with four 150-h.-p. continuous-current motors, the other with four single-phase 
115-h.-p. motors, that is, simply the complete motor trucks, we find that the weight 
of the continuous-current motor equipment would be nearly 26 tons, as against 27 
tons for the alternating-current equipment.” 

Carter, in reply, pointed out that Dawson was in error in stating that the alter- 
nating-cuirent motor is rated on the same basis as a continuous-current motor, and 
stated that the 115 li.-p. motor referred to by Dawson cannot be rated any higher than 
90 h.-p. through the gears if the temperature rise is limited to 75°C. after 5 a run of 
1 hour s duration at its rated voltage under the conditions prescribed by the American 
Institute rule. 

This gives for the two cases— 

Continuous-current motor . .18 kilogrammes per horse-power ; 

Single-phase motor . . . .27 

The trucks compare as follows : — 

iiuck equipped with four continuous-current motors weighs 44 kilogrammes per horse-power. 

” » >> single-phase „ ,,75 

Schoepf, in the discussion, gave the following as the weights of 150-h.-p. motors 
of the two types : — 

2'5 tons for a 150-h.-p. continuous-current motor. 

2*4 ,, ,, single-phase motor. 

Gaiter pointed out that the latter of these two motors was rated on the basis of a 
temperature rise of 75 degrees Cent, at the end of a 1 hour’s run on a 250-volt 
continuous-cm i ent circuit, and that it would have a far lower rating if based on a 
temperature rise of 75 degrees Cent, after a 1 hour’s run on a 250-volt alternating 
current circuit. In the course of his reply, Carter gave the figure of 2'15 tons as 
the weight of a certain 175 h.-p. motor in common service to-day on the Boston 
Elevated Railway. This is 12'5 kilogrammes per horse power. From the above 
particulars w 7 e obtain the data in Table CXIX. 


Table 


CXIX.— Weight of Single-Phase and Continuous-current Motors. 


Type. 

Rating of One Motor 
when based on standard 
one hour 75 deg. cent, 
basis when operated 
from appropriate 
circuit of normal volt¬ 
age of Motor. 

Weight of One 
Motor including 
Pinion. 

Weight of One 
Motor per H.-p. 

Weight of Truck 
equipped with 
two of these 
Motors. 

Ditto per 
Rated H.-p. 


Dawson . 

150 h.-p. 

2‘7 tons. 

18 - 0 kgs. 

18'5 tons. 

44 kgs. 

Cont. 

Curr. 

Schoepf . 

150 h.-p. 

2 - 5 tons. 

16 - 7 kgs. 




Carter 

175 h.-p. 

2 - 2 tons. 

12-5 kgs. 



Single Phase 

90 h.-p. 

2'4 tons. 

26-7 kgs. 

13 tons. 

75 kgs. 


Note.—One kg. = xtt&v of one metric ton. 


389 

















































ELECTRIC RAILWAY ENGINEERING 


Gearing increases the above motor weights by 10 to 15 per cent. Auxiliary 
equipment, in the case of the continuous current system, amounts to some 4 to 6 
kilogrammes per rated horse-power of the motors. It is highly improbable that for 
single-phase equipments, the auxiliary equipment weighs less than 10 kilogrammes per 
(correctly) rated horse-power of the motors. 

Schoepf, in the course of the discussion, also quoted some figures which, rightly 
considered, indicate the great equipment weigh incident to the single-phase system. 
He gave the weight of the single-phase equipment of a motor-coach, suitable for use 
on the suburban lines of the London, Brighton and South Coast Railway, as 31,000 lbs., 
and the continuous-current equipment of the motor-coaches used on the Metropolitan 
Railway as 29,500 lbs. Since on the former system, two motor-coaches are required 
for a 3-coach train, and on the latter, two motor-coaches for a 6-coach train, the 
coaches being of practically the same size in the two cases, it follows that the single¬ 
phase equipment for a given train is more than twice as heavy as the corresponding 
continuous-current equipment for this class of service. 

The service capacity of the single-phase motor is even lower, for its weight, in 
comparison with the continuous-current motor, than the hourly rating would indicate. 
In the hour run the greater part of the heat is expended in raising the temperature 
of the motor and but little is dissipated, whilst the final temperature attained in 
service depends on the rate at which the heat can be dissipated by the motor. The 
heavier the motor the greater will be its capacity for heat and the higher it will rate; 
but the increased weight does not involve a proportional increase in.dissipative power, 
and accordingly the service capacity is low for the rating. Comparison on the basis 
of a definite temperature rise after 1 hour’s run, therefore, is too favourable to the 
single-phase motor. 

It is thus evident that the single-phase railway motor is greatly handicapped as 
regards weight. The seriousness of this disadvantage is made the more apparent by 
reference to the curves in Fig. 358 (facing p. 384). For the single-phase motor the 
areas in that figure will be much more restricted. On the other hand, with high 
tension continuous-current motors, or with polyphase induction motors, the areas will 
increase. 

Thus from the standpoint of its technical merits, the single-phase commutator 
motor is at present a factor in the railway electrification problem only in so far as the 
possibility of its further improvement at an early date entitles it to consideration. 
Although the last three years have witnessed the advent of several types of single¬ 
phase commutator motor, each of which constitutes a great step in advance of the old 
induction type single-phase motor without commutator, there is still a wide gap to be 
bridged before it can, on the basis of its engineering merits, rival the continuous- 
current motor. The single-phase motor has the non-technical advantage that it is 
now fully realised that some radical innovation is essential to the success of 
railway electrification, and it appeals to the speculative instincts in human nature 
to take up a promising novelty rather than to undertake radical but comparatively 
uninteresting modifications of a well-tried and reliable system, especially as 
there is a prevailing belief that this would only postpone the inevitable, ultimately 
successful, introduction of the alternating current railway motor. It will, however, 
not be denied that a treble or quadruple increase in the traditional continuous-current 
trolley voltage would permit of greatly increasing the practicability of introducing 
electric traction on main line railways without discarding continuous-current railway 
motors. 


< 


390 


LOCOMOTIVES AND MOTOR CARRIAGES 

The single-phase commutator motor is not readily understood from an abrupt 
description of the motor as it now stands developed. It is instructive, and conduces 
to a better understanding of this motor, to trace the evolution of the ideas which 
have culminated m its inception. The polyphase induction motor first attracted 
general attention fifteen years ago, on the occasion of the Frankfort Exhibition. 
The simplicity of its construction, and especially the absence of a commutator, 
at once led to very optimistic predictions as to its rapid and ultimately universal 
adoption for all work for which electric motors are required. The polyphase induc¬ 
tion motor was found to have high efficiency and high starting torque. The depen¬ 
dence of a high power factor upon the use of an excessively small air gap, was 
felt to be a comparatively trifling drawback to set against the otherwise excellent 
mechanical design. In America the induction motor was built rather large and heavy, 
vith a leasonably deep air gap, and with partly or completely open slots and form- 
wound coils. In consequence of these concessions to the requirements of a rugged 
construction, it had a somewhat lower power factor than the European induction 
motors, which were built with an excessively small air gap, hand-wound coils, and 
with a minimum of material. A disadvantage of the polyphase induction motor, much 
moie seiious than poor power factor and small air gap, soon came to be recognised. 
This related to the inefliciency with which variable speed could be obtained? The 
simplest method consisted in the introduction of resistances in the rotor circuits, but 
this involved great sacrifice in efficiency. The efficiency decreased in direct proportion 
to the speed, so that at one-quarter or one-half full speed, the efficiency was respec¬ 
tively 25 and 50 per cent, of the full speed efficiency. The first suggestions for 
employing the polyphase induction motor for traction work, were met with this 
objection : that variable speed could not be economically obtained. This led to the 
development of the then so-called “ concatenated ” system of motor control. This is 
now designated ‘-'cascade " control, and consists in the use of a main motor and an 
auxiliary motor. For full speed the main motor alone is in circuit; for half-speed 
the main motor supplies half its energy mechanically direct to the train, and the 
othei half electrically from its secondary to the primary of the auxiliary motor. 
This system is exploited by the firm of Ganz & Co., ‘of Buda-Pesth, and is in 
successful operation on the Valtellina Railway in Northern Italy, and on other 
less important roads. It permits of regenerative braking above half-speed. The 
chief objections to this system, in addition to the still grave limitations to efficient 
speed control, are the small air gaps of the motors, their low power factor, the 
weight and cost of the auxiliary motors, the complicated control connections, and 
the need for at least two trolley wires or rails, and for a corresponding number 
of trolleys or contact shoes. This system has the great advantage of employing 
three-phase motors, which, for a given output, may be built lighter and cheaper 
than continuous-current motors, and, for high rated speeds, are more efficient. At a 
sufficiently low periodicity, the power factor is very high, and all the properties are 
greatly improved. Of course, the main advantage is that inherent to all alternating 
current systems : the facility of transformation, which permits the use of high 
voltage transmission lines, and thus of the economic transmission of electric energy 
over long distances. 

On the now historical high speed railway tests at Zossen, near Berlin, we again 
find three-phase motors employed, but not with concatenated connection. Little 
significance is, however, to be attached to this latter circumstance, since these tests 
were made more with a view to establishing the practicability of attaining high speeds, 

39i 


ELECTRIC RAILWAY ENGINEERING 

and of collecting the high voltage electric current at these speeds. Patent considera¬ 
tions probably also affected the choice of system. 1 

The speed-torque characteristic of the polyphase induction motor is unfavourable 
for traction in that its inherent property of running at constant speed independently 
of the torque, imposes far heavier peaks of load upon the generating station and on 
the line than are imposed by the continuous-current series motor, in which the speed 
falls off as the torque increases, thus equalising the load to a considerable extent. 
This inferiority of the polyphase induction motor becomes greatly accentuated in main 
line work with heavy trains running at high speeds at great distances apart, and would 
easily lead to requiring power-house installations capable of supplying twice as high 
peaks of load as would be required of power-house installations for roads employing 
motors with the speed-torque characteristic of the continuous-current motor. 

The constant speed characteristic of the motors has the further practical dis¬ 
advantage of confining their use to trains drawn by a single locomotive or motor- 
coach. In operation the driving wheels are worn down by some 8 per cent, before 
being retyred, and if a train were drawn by two units, one with new wheels and the 
other with worn wheels, the motors on the former might be running 8 per cent, slower 
than those on the latter, taking practically all the load, and possibly driving the 
others as generators. 2 This prevents the promiscuous mixing of motor stock which is 
inevitable where a multiple unit system is employed. 

The chief faults of the three-phase motor for railway electrification, may be 
summed up as follows:— 

(1) Constant speed characteristic ; 

(2) Necessity for at least two trolleys ; 

(3) Small air gap ; 

(4) Low average power factor. 

From the very earliest days of three-phase motor developments it has been known 
that, once started, a three-phase motor will continue to run when one of the three 
circuits leading to it is opened. It thus operates as a single-phase motor. This pro¬ 
perty is used on three-phase railways at points where the nature of the line does not 
permit of more than one trolley. It was also known that a three-phase motor would 
start as a single-phase motor, if, with one of its windings short-circuited, another was 
thrown on the line. Why then is not the first of the above-tabulated objections, i.e., 
the need for more than one trolley, thereby overcome ? It is not overcome for the 
reason that this pure induction-type single-phase motor has exceedingly weak starting 
torque, and far lower capacity than when operated three-phase, a lower average power 
factor, and greater heating for a given load. Nevertheless, the need for a single-phase 
motor was believed to be so acute, that every attempt was made to improve the proper¬ 
ties of the pure induction-type single-phase motor without a commutator. At the end 
of ten years of effort, nothing in the remotest degree approaching a commercially 
satisfactory motor had been produced on these lines. 

Matters were in this state in the beginning of the year 1901. In this year, 
Heyland and Latour independently demonstrated the practicability of operating three- 
phase motors at unity power factor at some one load, by the addition of a commutator 


1 It is notable that Reichel, who was prominently associated with the design of the Siemens and 
Halske equipments and with the conduct of these Zossen tests, is now an advocate of the employment 
of the continuous-current motor for railway electrification. 

2 See Carter, “Elec. Rev.” Yol. 54, p. 868. Also “ Jour. Inst. Elec. Eng.” Yol. 86, p. 256. 

392 


LOCOMOTIVES AND MOTOR CARRIAGES 

t l t fl he i r °w’; thU ! living arrangements more or less resembling those proposed in 
1888 by Wilson (see British Patent No. 18,525 of 1888) and reinvented, tested, and 
set aside by Gorges in 1891. The light thrown by these investigations of Heyland 
and Latour on the properties of polyphase induction motors and the formulation by 
Latour of the closely related conception of the panchronous operation of generators 
were soon followed by another very important advance, namely, the invention by 
Winter and Eichberg of an economical means of controlling the speed of three-phase 
motors. By means of brushes bearing on a commutator, these inventors supplied 
current to the rotor windings of an ordinary polyphase induction motor, ushm a 
variable voltage source, such as a variable ratio transformer or, and generally prefer¬ 
ably, an induction regulator. The rotor speed is inversely proportional to the voltage 
applied at the brushes. This invention would undoubtedly have led to renewed 
activity in the use of three-phase motors for railway electrification, in spite of the 
double-trolley difficulty, had not Lamme 
in Pittsburg, U.S.A., already announced 
the success of a single-phase railway 
system in which a series-wound, 
laminated field, commutator motor was 
employed. At any rate, Latour in Paris 
and Winter and Eichberg in Vienna 
and Berlin soon evolved from this 
variable speed idea a type of single¬ 
phase commutator motor which, however 
great its faults, is a tremendous advance 
on the induction type of single-phase 
motor without commutator. 



The Repulsion Type of Single-Phase 
Commutator Motor. 


Magnetising 

Component 


/Repulsion Motor (Elihu Thomsen) 

For /Analytical Purposes it is 
Instructive to replace the above 
diagram by I he following diagram in 
which the field Winding is- 
1 conceived to be decomposed 
into two Component 

t/indinjs 





Energy Component 
of Circuit 


Fi 


l S . 360.—Diagram of Repulsion 
Type Single-Phase Motor. 


are 


A form of single-phase commutator 
motor which has been proposed and 
tried for railway work, is the so-called 
repulsion motor. This was invented 
many years ago by Elihu Thomson at 
Lynn, U.S.A., and has been employed 

to some extent where small stationary motors, having series characteristics, 
required. 

It is shown diagrammatically in Fig. 360. It has the advantage of having no 
conducting connection between the armature and power supply, so that the field may 
be wound for high potential, although this entails extra weight and expense on 
account of the space required for the heavier insulation between field turns. Another 
advantage of the lepulsion motor is that it cannot flash over at the commutator, since 
the blushes aie shoit circuited. Tor reversing the direction of running and for 
regenerative braking, either the brushes must be shifted, or more or less complicated 
control of the stator connections must be employed. This motor has an effective range 
of speed fiom low speeds up to about 25 per cent, above synchronous speed, above 
which the commutation is unsatisfactory. 

In 1903 the repulsion motor was taken up for alternating current traction work. 

393 
















ELECTRIC RAILWAY ENGINEERING 


The results obtained indicate that it has a fair average power factor, but considerable 
rotor losses and a somewhat low specific starting torque. It now appears to have been 
abandoned in favour of the Latour-Winter-Eichberg and the Lamme types of motor. 


The L. W. E. Type of Single-Phase Commutator Motor. 

The Latour-Winter-Eichberg single-phase motor which is shown diagrammatically 
in Fig. 861, resembles the repulsion motor in having short-circuited brushes on the 
commutator under the poles; in having an effective range of speed for practical work 
from low-speed to a little above synchronism, and in having rather excessive rotor 
losses. It may in fact, as far as its main action is concerned, be regarded as a 
repulsion motor in which, instead of the brushes being shifted to change the direction 
or magnitude of the torque, the exciting field is shifted by the introduction of a cross 



Fig. 361. Diagrams of the Latour-Winter-Eichberg Type of Single-Phase 

Commutator Motor. 

The diagram at the left shows the arrangement without a transformer. 

>> ,, right „ ,, ,, with „ 

In the Latour-Winter-Eichberg type the compensation is obtained by the induced current in the armature between the 
short-circuited brushes. 


field in phase w 7 ith it. This auxiliary field is produced by introducing into the 
armature, through brushes at the neutral points, either the main power current, or a 
current proportional to the same, taken from a series transformer. The two alternative 
arrangements are shown in Fig. 361. The latter of these has the following advantages 
over the former : (1) There is no conducting connection between armature and power 
supply, so that the stator can be wound for high, or any desired pressure. (2) The 
motor characteristics can be varied by varying the ratio of the auxiliary transformer 
on the secondary side, which involves dealing only with small currents at low voltage, 
and affords an exceedingly safe and flexible method of control. With reference to the 
first of the above advantages, it has not usually been considered desirable to wind these 
motors direct for line pressure, the excessive vibration to which they are subject, and 
the impracticability of having them under continued expert supervision, rendering it 
practically necessary to insert a main transformer between line and motors so as to 
confine the region of high potential to the simplest and most reliable of appliances. 
The motors now being built by the Allgemeine Elektricitats Gesellschaft for the 
youth London line of the London, Brighton and South Coast Railway, are of the 

394 



















LOCOMOTIVES AND MOTOR CARRIAGES 

Winter -Eichbeig type, and a main transformer is included in the equipment between 
the line and motors, the latter being wound for a reasonably low voltage. 

. , The Winter-Eichberg type of motor, which is supplied in this* country by the 
nfcish Thomson-Houston Company, consists of a stator more or less resembling that 
of an ordinary polyphase induction motor, and carrying a single-phase winding. The 
rotor is similar to the armature of a continuous-current machine, except that the 
commutator is larger in proportion. Short-circuited brushes bear on the commutator 
at the centre of the poles, and exciting brushes at the neutral point. There is thus 
rather a large amount of brush gear, and the losses due to brush friction and contact 
resistance are somewhat excessive—requiring a large commutator, which in any case 
is very liable to run hot. 


The Compensated-Series Type of Single-Phase Commutator Motor. 

The compensated-series type of alternating current railway motor is a develop¬ 
ment of the series motor as used for continuous currents. The latter motor, it' 
piovided with a completely laminated magnetic circuit, could be operated from an 
alternating-current power supply, but necessarily offers so high an impedance as to 
have an exceedingly low power factor, whilst very poor commutation is to be expected, 
and altogether such a motor is impracticable, except in very small sizes. Recognising 
the need of diminishing the effect of armature reaction in this type of motor, Lamme 1 
intioduced longitudinal slits or holes in the pole pieces, in order to impose reluctance 
in the path of the armature flux, and in some of the holes placed copper bars, con¬ 
nected together so as to form short-circuited coils at right angles to the armature flux, 
the current induced in which tends still further to cut down the cross-magnetisation of 
the armature. In order to improve the commutation of the machine, Lamme adopted 
the well-known expedient of inserting high-resistance leads between the armature coils 
and the commutator bars. Finzi, of Milan, independently investigated the series motor 
for traction purposes, and also adopted the expedient of dividing the pole pieces across 
the path of the armature flux, and of inserting high-resistance commutator leads, but 
did not employ compensating coils. His motor is, therefore, not a compensated motor, 
but nevertheless appears satisfactory for small tramway sizes. Shortly after this, the 
General Electric Company of America took up the development of the alternating- 
current series motor, and their engineers appear to have been amongst the first to fully 
realise the importance of the arrangement of the compensating winding. Instead of 
bunching this in one slot in the centre of each pole, as in Lamme’s motor, they dis¬ 
tributed it uniformly over the stator face, connecting it in series with the armature, 
and arranging to have practically the same number of ampere-conductors per unit of 
peripheral length in the compensating as in the armature winding. The com¬ 
pensating winding was of course connected so as everywhere to oppose the armature 
field with an equal field, thus completely neutralizing the armature reaction. The 
distributed compensating winding has now been generally adopted for this type of 
motor. 

The compensated-series type of motor, which is shown diagrammatically in 
Eig. 362, is distinguished from the above-mentioned repulsion types in having its 
range of practicable and efficient speed, from synchronism to some two or two and a 
half times synchronomous speed. Its efficiency is somewhat higher than, whilst its 


1 See British Patent 2,746. 1902. 

395 


ELECTRIC RAILWAY ENGINEERING 



\ li Magn etising 

Apsr' 


average power factor is quite as high as, that of the Latour-Winter-Eichberg type, 

and considerably higher than the pure repulsion type. 
Compared with the continuous-current series motor, it has 
a rather weak field and proportionally large armature 
reaction, which is taken care of by the compensating field. 
This type of motor is well suited for use as a continuous- 
current motor, although for this purpose it is of advantage 
to employ a stronger field. The General Electric Company 
of America have accordingly adopted the practice of winding 
the exciting coils in sections, which are put in series for 
continuous-current working and in parallel for alternating- 
current working. As a continuous-current motor, the com¬ 
pensated series motor has a higher efficiency and greater 
capacity than when used as an alternating-current motor, 
although it falls short of the ordinary continuous-current 
railway motor in these respects. 

The following description of the motor and its auxiliaries, 
and of the method of control, applies to a 75 h.-p. motor 
designated G.E.A. 605, as manufactured by the General 
Electric Company in America, and by the British Thomson- 
Houston Company in England. The motor is illustrated in 
Figs. 363, 364, 365, and 366, and an assembly drawing 
giving the main dimensions is shown in Fig. 367. 

It is designed to operate at from 200 to 250 volts, 
taking power at a frequency of 25 cycles per second. The rating is 75 h.-p. at 


Compensator) 

Fig. 362. Compensated 
Series Type of 
Single-Phase Com¬ 
mutator Motor. 

(Westing-house (Lamme). 
—The compensation is 
obtained, by the current 
in the stationary series 
windings wound in slots 
in the surface of the pole 
shoes and in quadrature 
with the main field wind¬ 
ing. In the earlier form, 
the compensation was 
obtained by the current 
induced in a compensating 
winding short-circuited on 
itself.) 



Fig. 363. Assembly of British Thomson-IIouston Co.’s Compensated Series 

Single-Phase Pailway Motor. 

Rating as a continuous-current motor on the one-hour 75 deg. Cent, standard, is 75 h.-p. at 200 volts. 

396 










LOCOMOTIVES AND MOTOR CARRIAGES 

■200 volts when operating as a continuous-current motor, and on the basis ol 75° Cent. 



Fig. 304. 


Assembly of British Thomson-Houston Co.’s Compensated Series 
Single-Phase Railway Motor. 



rise after one hour’s run, as defined 
Committee of Standardisation. 1 

The frame of the motor is 
made of steel and is split dia¬ 
gonally, the two sections being 
bolted firmly together. The frame 
encloses and holds securely the 
laminated field structure. At the 
ends of the frame are large bored 
openings, into which malleable 
iron frame heads carrying the 
armature shaft bearings are bolted. 
Through these openings, the 
armature is put in place or 
removed from the frame. 

A large aperture is provided 
in the frame above the commu¬ 
tator, through which the com¬ 
mutator can be inspected or 
the brush gear adjusted. The 
opening is closed by a malleable 
iron cover with a felt gasket 
—the cover being held in place 


l>y the American Institute of Electrical Engineers 


Fig. 36.5. Field for British Thomson-Houston Co.b 
Compensated Series Single-Phase Railway Motor 

by a quickly adjustable cam-locking device. 


1 Transactions A.M. Inst. Elec. Engrs., Vol. XIX., p. 1083. 

397 








ELECTRIC RAILWAY ENGINEERING 


The field laminations are of the induction motor type, the windings being 
distributed around the inner face in such a manner as to give a four-pole stator. A 



Fig. 366. Parts of British Thomson-Houston Co.’s Compensated Series 

Single-Phase Railway Motor. 

portion of these windings is used for excitation, whilst the remaining portion is 
connected directly in series with the armature, and is so placed and w T ound as to 



Fig. 367. Assembly Drawing giving the Main Dimensions of British Thomson-Houston 
Co.’s 75 h.-p. Single-Phase Compensated-Series Type Railway Motor. 

398 





























































































































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 

d^ y n r“r the ar r ature leaction ’ which would otherwise cause field 
stoi ion and result in sparking at the commutator. The compensating winding 

also materially improves the power factor, by reducing the inductive drop. The 
exciting windings are arranged in two circuits, which are connected in parallel for 
alternating-current operation, and in series for continuous-current operation The 

:r: :v:r ate aSbeS ‘° 8 ’ an<1 8 P eciall y Prepared fabric, which makes 

t semi-liiepioof and practically impervious to moisture. 

The exciting field has ‘24 turns, wound in 24 brass slots spaced so as to form 

Lh° W field has 60 turns W0Und in 60 slots in laminations 

listiibuted uniformly over the pole face. Dimensions of the slots : 1*47 in. by 049 in 

J ^ Vn' K ® r< L = . 86 Per Cent * B ° fch com P en sating and exciting windings are 
made of 0‘5 in. x 0T2 in. copper bar. 8 

The armature closely resembles the standard continuous-current railway armature. 
The connection is four-pole multiple drum, and the armature is bar wound—a large 
number of single-turn coils being employed for the purpose of improving the com¬ 
mutation. The. bars are separately insulated with mica and are assembled in sets, 

w lie i are then insulated as a whole with mica, and covered with an outside protective 
covering of specially prepared tape. 

Tbe diameter of tbe armature is 16 in., the gross core length 19 in., there beinv 
o5 slots each, of size 1'59 in. x 0-54 in. There are no ventilating ducts provided 
m the armature. 

The radial depth of iron below the slots is 2*41 in. The winding has one turn 
per coil and 6 conductors per slot, the size of the conductor being 0*55 in. x Oil im 
The average length of air gap is Oil in. 

The construction of the commutator is similar to that of standard continuous- 
current railway motors. The segments are of hard drawn copper, insulated throughout 
with the very best grade of mica, of such hardness as to wear down evenly with the 
copper. . The commutator ears into which the armature conductors are soldered are 
fonned integial with the segments. The diameter of the commutator is 13‘25 in. 
and it has 165 segments. 

There are four brush holders, mounted on a revolving yoke, and each containing 
foui carbon brushes. The holders are made of cast bronze, and are supported on 
mica-msulated studs, bolted to the revolving yoke. The brushes slide in finished 
ways, and are pressed against the commutator by independent fingers, which mve 

practically uniform pressure throughout the working range of the brush. The size of 
brush is 1|- in. by f in. 

The frame heads carrying the armature shaft bearings are extended in cone 
shape well under the commutator shell and pinion-end armature core head This 
construction forms a support for the bearing linings, which are very strong and rigid. 
The heads have large oil wells, into which oily wool-waste is packed and°comes into 
contact with a. large surface of the armature shaft, through an opening cut in the 
low pressure side. of the bearing linings. The armature shaft linings are unsplit 
bronze sleeves finished all over, having a thin layer of babbitt metal soldered to 
the interior. The babbitt furnishes an ideal bearing surface, and is so thin that 
it does not allow the armature to rub on the poles in case it is melted out by over¬ 
heating. Waste oil is prevented from reaching the vital parts of the motor by 
means of a series of oil deflectors, which throw the oil into large grooves cast in 
the bearing heads, from which it is conducted to drip-cups cast on the outside of 
the heads. The bearing boxes are practically the same as standard car axle boxes 

399 


ELECTRIC RAILWAY ENGINEERING 

and are reached through large hand holes protected by swing covers, held in place 
by springs. 

The axle linings are in two segments and are held in place by cast steel caps, 
which are tongued and bolted to planed and grooved surfaces on the frame. Large 
oil wells are cast in the caps, into which is packed oily wool-waste which comes into 
contact with a large surface of the axle through openings cut in the bearing linings. 

The gear is made of a superior grade of cast steel, and contains 73 teeth of 
3 diametral pitch. It is of the split type, accurately bored and provided with a 
keyway for securing to the axle. The pinion is of forged steel, extra hammered to 
improve the quality of the metal. It contains 17 teeth, and has a taper fit on the 



Fig. 368. G.E.A. 605 Railway Motor. Characteristic Curves on 250-volt Alternating- 
Current Circuit, 25 Cycles. Efficiency Corrected for a Copper Temperature of 
75° Cent. 33-inch Wheels 73/17 Gear. (British Thomson-IIouston Co.) 


armature shaft of § in. to the foot measured radially. The gear ratio is 4'3. The 
gear case is strongly made of malleable iron, with a substantial form of support. 

The following are the weights of the motor, excluding pinion, gear, and 
gear case :— 


Frame . 
Field . 
Armature 


1,934 lbs. 
1,217 lbs. 
1,143 lbs. 


Total 


4,294 lbs. 


The characteristic curves of this motor are shown, for alternating-current 
operation, in Fig. 368, and for continuous-current operation in Fig. 369. 

400 








































































LOCOMOTIVES AND MOTOR CARRIAGES 

I he method of control applied to these motors is shown diagrammatically in 
Tig. 370, which shows the connections for four motors with controller and compensator. 



.Fig. 369. G.E.A. 605 Railway Motor. Characteristic Curves oh 250-volt Continuous- 
Current Circuit. Efficiency Corrected for a Copper Temperature of 75° Cent. 
33-inch Wheels 73/17 Gear (British Tiiomson-ITouston Co.). 


For alternating-current working, the motors are connected permanently in series, the 
circuit connections leading first through the field windings of the four motors, and 
then in series through the armatures and their compensating windings. 

E.R.E. 401 


D D 










































































































































































ELECTRIC RAILWAY ENGINEERING 


The speed variations are obtained by varying the voltage across the group of 



Fig. 370. Cab Wising foe T— 33 A Controllers with Four G.E.A. 605 Compensated 
Motors for A.C. Operation(British Thomson-IIouston Co.). 


four motors, by connecting with different taps of the compensator or auto-transformer. 
The latest form of compensator is shown in Fig. 371, and is of the oil-cooled type. 



Fig. 371. British Thomson-Houston Co.’s Latest Form of Oil-Cooled Compensator, 
as Employed in Single-Phase Bailway System. 

402 


































































































LOCOMOTIVES AND MOTOR CARRIAGES 

A diagram of connections for a multiple-unit system of control is shown in 
Dg- 372, in which the various circuit connections are made by means of contractors 



Fig. 373. Diagram of British Westingiiouse Electric and Manufacturing Co.’s Single- 
Phase Series Motor, with Forced Neutralising Winding, and Showing Normal 
Distribution of Magnetic Flux. 


403 


D D 2 
































































































































































ELECTRIC RAILWAY ENGINEERING 

energised by a small master controller, instead of being made directly by the 
controller. 

This motor, in common with, others of this type, will operate equally well on a 

Z 

Q_ 



300 500 700 900 l lOO 

AW1PLRE.5 

Eig. 374. Characteristic Curves of British Westinghouse Electric and 
Manufacturing Co.’s Standard Single-Phase Railway Motor. 

continuous-current circuit. The modifications which are necessary for adapting the 
equipment for continuous-current working from a 500 to 600 volt circuit, consists in 

404 


























































































































































































































































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 


grouping the motors in sets of two, connected in series, and operating the groups in 
series or in parallel by means of the ordinary series parallel control. A special 
commutation switch is employed for making the necessary changes in connections in 
passing from alternating to continuous current working, or vice versa. 

In the Westinghouse system the high voltage line current is reduced to a suitable 
pressure for use by the motors, by means of an auto-transformer. The motors 
themselves are of the series type with forced neutralising winding embodied in the 
stator, illustrated in diagrammatic form in Fig. 373. In general, with good climatic 
conditions and line voltages up to about 6,600, the air blast type of transformer is 



Gr-oivnc/ 


Sequence of Sm/ahes 


K Ci 

w 


/ 

ft 










• | 

2 

ft 




ft 






•1 

3 

• 



• 

9 






ST 

■V- 

• 


• 

• 

9 







/ 


• 




© 



• 


-v 



• 



ft 



• 


n* 

Z 



• 




• 


« 


i* 

3 


• 





• 


• 


A 



c 






c 



r 

6' 



• 





• 

• 




/->y /YoVche S 


Fig. 375. British Westinghouse Electric and Manufacturing Co.’s Single-Phase Motors 
and Control Equipment Connections for Working on Alternating-Current or 
Continuous-Current Circuits. 


used, whilst with higher voltages or bad climatic conditions, such as working in 
damp tunnels, etc., the oil insulated, self-cooling type of transformer is used. 

Figure 374 shows curves of speed torque, power factor, efficiency, and horse-power 
for the standard 150 h.-p. Westinghouse motor. 

No change is made in the motor for working on alternating or on continuous 
current. The neutralising winding on the field frame is permanently in series with 
the armature, and is retained in use whilst working on continuous current since it 
tends to improve the commutation of the motor under that condition. Fig. 375 
shows the connections of the motor and control equipment for working on alternating 
and on continuous current. 

Figure 376 shows the connections for multiple-unit train control. 

In the 150 h.-p. motor the weight of the stator is approximately 3,900 lbs. and 
that of the armature approximately 1,500 lbs. The pinion, gear, and gear case weigh 

405 










































































ELECTRIC RAILWAY ENGINEERING 



406 


3rf(». British Westinghouse Electric and Manufacturing Co.’s Wiring Diagram for a Motor Coacii equipped 
with Single-Phase Series Motors and Electro-Pneumatic Multiple-Unit Control System. 


































































































































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 

about 600 lbs., making the total weight of the motor complete about 6,000 lbs. This 
motor is designed for working both on alternating and continuous current. 

The motor is of the single-phase series wound railway type, designed to operate 
with alternating current, and has speed and torque characteristics similar to those of 
a continuous current series motor. The voltage applied to the motor is about 250 to 
260 volts as against 620 volts for continuous current motors. This considerably 
reduces the liability of damage to insulation. 

The nominal one-hour rating is 150 h.-p. At this load, when supplied with 
alternating current at 260 volts 25 periods per second, the motor is stated to take 
670 amperes and will have an efficiency of 89 per cent, and a power factor of 88*5 per 
cent, at a speed of 570 r.p.m. Under these conditions the temperature rise, after a 
one hour’s run on the testing stand, is stated not to exceed 75° C. by thermometer 



Fig. 377. Armature of British Westinghouse Electric and Manufacturing Co.’s 

150 h.-p. Single-Phase Bailwaa' Motor. 

measurement. The continuous capacity of the motor is given as 330 amperes 
at 125 volts. 

The motor frame consists of a cast steel yoke into which soft steel panellings are 
dovetailed and securely clamped, producing a magnetic circuit which is completely 
laminated. 

There are six brush holders, each with two carbon brushes, the current density 
in which, at normal rated load, is 65 amperes per square inch. Flexible shunts are fixed 
to the brushes to relieve the springs from carrying current. The brush holders are 
adjustable, thus allowing compensation for the wear of the commutator. 

The motor is held on the axle by means of axle caps split at an angle of about 
35°, the caps being below the axle and the frame above. The opposite side of the 
motor is arranged for nose suspension. 

All the bearings are made of phosphor bronze and are arranged for oil waste 
lubrication, having oil reservoirs of ample capacity. The armature bearings are 
4 in. X 7f in. and in. X lOf in. respectively. 

407 














ELECTRIC RAILWAY ENGINEERING 


There are six main field coils wound with copper strap and insulated with mica. 
Each coil is held rigidly in position on its pole by hangers, independent of the 
pole pieces. 

The neutralising winding consists of copper bars placed in slots in the pole faces, 
and is insulated in the same way as for the main field coils. This winding is so 
arranged that it need not be disturbed when removing the field coils. 

The armature core is built up of soft steel punchings assembled on a cast iron 
spider. The shaft, which is made of open hearth steel, is pressed into the spider 
with a pressure of from 20 to 30 tons and is also secured by steel keys. The winding 
is placed in partially closed slots in the core with three layers in each slot, one of 



Fig. 379. Field Frame oe British Westinghouse Co.’s 150 h.-p. Single-Phase Railway 
Motor with the Neutralising Windings only in place. 


which constitutes the lead to the commutator, and has relatively high resistance, 
which acts as a preventive lead whilst the coil is being short-circuited under the 
brushes. Each conductor is insulated along its entire length by overlapping layers 
of mica tape, and each group in each slot is further insulated from the core by being 
supported in a moulded mica cell. The completed winding is held firmly in position 
on the core by insulated wedges, and the ends are banded down on the coil supports. 

The commutator is made of rolled and hard drawn copper, clamped in Y-shaped 
cast steel rings. The insulation between the bars is formed with specially prepared 
material of such hardness as to ensure its wearing at the same rate as the copper. 
The complete commutator is pressed on the spider which holds the armature core. 

The photograph in Fig. 377 shows the complete armature. 

The pinion is made of forged steel with machine-cut teeth, and the gear wheel 

408 





) 



Fig. 378. Outline Drawing of 150 h.-p. Single-Phase Series Wound Kailway Motors, as 
Manufactured by the British Westinghouse Electric and Manufacturing Co. 











































































































































































































































































































































































































































t 


LOCOMOTIVES AND MOTOR CARRIAGES 


The gears have a diametrical pitch 


is made of cast steel with machine-cut teeth, 
of 2^ in. and 5 in. width of face. 

2,000 I loL S ltr„itgKMT leted "’ in St “ n<1 a « of 


in 


Figure 378 shows an assembly 
Figs. 379 and 380 show the field 


drawing of the motor, whilst the photographs 
frame. The former shows the frame with the 



Kg. 38°. Field Frame op British Westinghoose Co.'s ISO h,p. Single-Phase Bailway 
Motor with both the Neutralising Windings and the Magnetising Coils in Place. 


/ ir Pos/rton 2"°Pas/ t/ on 


3 m Pos< t/ on 


P r ~Pos/r/on 


3 T “.Pas / T/ory 



&• 


381. Diagram, showing Relative Electrical Connections between Auto-Transformer 
and Preventive Coil and Voltages applied to Motors for the several Positions of 
Master Controller (British Westinghouse Electric and Manufacturing Co.). 

409 



















ELECTRIC RAILWAY ENGINEERING 


neutralising windings only in place, and the latter the frame with the field coils also 
in position. It will be noticed that the field coils can be removed without interfering 
with the neutralising winding. 

The function of the auto-transformer is to transform the line voltage, which in 



tlGfJT/J 


Fig. 382. Diagram, showing Distribution of Current with Controller in Second 
Position (British Westingiiouse Electric and Manufacturing Co.). 



Fig. 383. Diagram, showing Distribution of Current with Controller in Transition from 
Second to Third Position (British Westinghouse Electric and Manufacturing Co.). 

410 



Co/yr/foi L£ f 
































































LOCOMOTIVES AND MOTOR CARRIAGES 

practice varies from 3,300 volts to 18,000 volts, according to the magnitude of the 
undertaking, to the low voltage required by the motors (160 to 280 volts). The 
transformer is of the single-winding type, in which one end of the winding is connected 
to the trolley and the other is permanently connected to earth. At the earthed end 
of the winding, various taps are brought out, giving suitable voltages for supply to 
the motor terminals, as illustrated in Figs. 381, 382 and 383. Auto-transformers are 
usually made either of the air blast type, in which case the air blast is furnished 
by a small motor-driven fan mounted in the case of the transformer; or else of the 



Fig. 384. Photograph of the High-tension End of an Air-Blast Tape of Auto- 
Transformer, AS EMPLOYED IN TnE BRITISH WESTINGHOUSE Co.’S SiNGLE-PHASE RAILWAY 
System. 


oil-insulated, self-cooling type, in which case the transformer winding is wholly 
immersed in insulating oil carried in a metal case. 

The photograph in Fig. 384 illustrates the high tension end of an air-blast 
auto-transformer, and Fig. 385 gives the outline of an oil-insulated auto-transformer. 

The unit switches shown in Fig. 386 take current from the various low tension 
tappings of the auto-transformer and deliver it to the motors. These switches are 
caused to open or close by air pressure acting on small pistons. The compressed air 
is admitted to, or released from, each unit-switch cylinder by means of a small pin 
valve which is operated by an electro-magnet. The electro-magnet is controlled by 
the motormau by means of the master controller. The electro-pneumatic control of 
the unit switches is common not only to this system but to the Westinghouse con¬ 
tinuous-current railway controllers and the Westinghouse railway signalling system. 
With this system of control, the unit switches and reversers throughout a train are 
made to move in unison under the action of one master controller, by means of a 
small multicore cable which connects all the master controllers, switch groups, and 

4 11 




ELECTRIC RAILWAY ENGINEERING 


reversers, on a train in parallel. This multicore cable is joined up between cars by 
plug-and-socket and flexible connections. 

In operation, two of the unit switches are always closed whilst the master 


H T. Terrrurtofo 


L T Tcr~rr/'rafs 




Fig. 385. Outline Drawing of Oil-Insulated Auto-Transformer by tiie British 
Westinghouse Electric and Manufacturing Co. 


controller is on a running point, and the current which they furnish is led to the 
two ends of the preventive coil. 

The preventive coil is used for the reason that it permits the circuit to the 
motors to be maintained unbroken when passing from one voltage to a higher or 



Fig. 380. Electro-Pneumatically-controlled Unit Switches, as employed in the 
British Westinghouse Co.’s Single-Phase Bailway System. 

412 


































































































LOCOMOTIVES AND MOTOR CARRIAGES 

lo^ei \oltage tap, since two of the unit switches can be closed simultaneously without 
local currents between them being developed. 

dhe leveiser leceives current from the preventive coil and delivers it to the 



Fig. 


38“ 


British 3\estinghouse Co.’s Self-reversing Pt 


A.NTOGRAPH TROLLEY. 



motors Which are connected in parallel. The reverser is connected in such a way 
as to leveise the fields of the 

motors and not the armatures. 

The reverser is operated by 
means of air pressure acting on 
pistons controlled by electro¬ 
magnets on the same system as 
described above in the case of 
the unit switches. An interlock 
on the reverser makes it im¬ 
possible for any current to be 
delivered to the motors until the 
reverser has been thrown in the 
right direction. The movement 
of all the reversers on a train is 
effected simultaneouslv, as in 
the case of the unit switches, 
through the movement of the 
master controller. 

The master controller con¬ 
sists of a very small drum-type 
controller. The handle is moved 
to the right or left according to 
the direction in which it is 
desired to move the train. In 
Fig. 376 there is shown a dia¬ 
grammatic development of the 
master controller, in which the 
successive running positions, 


Fig. 388. British Westinghouse Co.’s Self-reversin' 
Pantograph Trolley. 


~ 7 

fiom one to five, are clearly indicated together with the different switch combinations 
Owing to the fact that the voltage on the motor terminals is varied by varying thi 


4i3 
















ELECTRIC RAILWAY ENGINEERING 


connections from the auto-transformer, and not by the interposition of resistance, 
as in the case of continuous-current railway practice, every notch on the master 
controller is a running notch, and the train can be held at the corresponding speed 
for any length of time without rheostatic losses. 

In the case of small cars operating at moderate speeds, a wheel type of trolley 
may be used, provided that it is thoroughly insulated from the car body. On the 
heavier types of vehicle and on locomotives the self-reversing pantograph trolley has 
been found most successful. Photographs of this type of trolley are given in 
Figs. 887 and 388. The pantograph type of trolley is suitable for the highest speeds, 
as, owing to its great width, there is no possibility of its jumping the trolley wire. 
The trolley is of the self-reversing type and is brought up into the running position 



Pig. 389. British Westinghouse Co.’s Exhibition Car at Trafford Park, Manchester. 

The car is equipped with the British Westinghouse Co.’s Single-Phase Railway System. 


in contact with the trolley wire, or withdrawn, so as entirely to isolate the car from 
the high tension supply circuit by means of air pressure. The control of this air 
pressure is effected by means of a special three-way cock fitted in the driver’s cab. 

Fig. 389 is a photograph of the exhibition car at the Trafford Park Works of 
the British Westinghouse Electric and Manufacturing Company. The car is equipped 
with four 100 h.-p. single phase railway motors and with the electro-pneumatic 
multiple-unit switch control. The trolley pressure on this exhibition line is 3,300 
volts, and the car is fitted with ammeters, voltmeters, and wattmeters for making 
complete observations. 


The several types of single-phase traction motor have been somewhat hastily 
reviewed, for, while their properties are of great interest, the fact of greatest present 

414 








































LOCOMOTIVES AND MOTOR CARRIAGES 

commeicial significance is that the net results are strikingly alike in all types. Their 
respective features of superiority and inferiority are of a minor character, and largely 
offset one another. Hence we may, in much of the following discussion, allude to 

the “single-phase commutator motor ” as having certain properties, without reference 
to the particular type. 

The single-phase commutator motor ” may be said to be characterised by the 
following features of inferiority :— 

A considerable loss by hysteresis and eddy currents in the stator, not present in 
the continuous-current series motor. 

In all types, a greater commutator loss due to the desirability, if not necessity, of 

employing a lower commutator voltage than is customary in the continuous-current 
motor. 

In the Latour-Winter-Eichberg motor, a still further commutator loss due to the 
extra short-circuited brushes. 

An efficiency at all loads, and particularly at light loads, considerably inferior to 
that of the continuous-current series motor. 

Commutation decidedly inferior, at any rate at starting with heavy torque, to that 
obtained in the continuous-current series motor. 1 

A considerably larger and more expensive commutator than is employed in the 
continuous-current motor. 

Chiefly on account of the larger internal losses, a considerably larger, heavier, and 
more expensive design in general, than for the continuous-current motor. 

A gieatei liability to breakdowns between turns in the field windings than in the 
continuous-current series motor, even when much more liberally insulated, and a 
temporary complete disablement of the motor when such a breakdown occurs, 
whereas in the continuous-current motor a short-circuited field turn does not disable 
the motor. 

A power factor averaging, in actual service, considerably less than unity. 

An amount of auxiliary apparatus on the train, greatly exceeding in weight and 
cost, that employed for the continuous-current series motor. 

By these means there have been obtained— 

A speed toique characteristic about equivalent to that of the continuous-current 
series motor. 

Regulation by voltage control, thus dispensing with rheostatic losses. 

Ability to transmit by high tension alternating current right through from power¬ 
house to train, any desirable intermediate transformations of voltage being accom¬ 
plished by means of stationary transformers, thus avoiding expensive and inefficient 
rotary converter or motor-generator sub-stations. 


1 The coil short-circuited under the brushes constitutes, at the moment the motor is thrown on 
the line, a stationary secondary circuit in which large currents are induced by the alternating magnetic 
Hux. As the motor starts, the armature turns successively occupy and depart from this position, and 
occasion considerable sparking as well as a considerable I.-R. loss. In discussing this point, Lamme 
states (American Institution of Electrical Engineers, January 29th, 1904)“ The short-circuit current 
at start is one of the most serious conditions which confront us in alternating current motors, and is 
also of great importance where there is any considerable operation on low speeds. The speaker 
advocates a type which he considers gives the easiest condition in this regard. This short-circuiting 
cannot be entirely avoided in any of the motors brought out, without adopting abnormal and ques¬ 
tionable constructions, although devices like narrow brushes, sandwich windings, etc., have been 
proposed.” 


415 


ELECTRIC RAILWAY ENGINEERING 


Although progress in the development of the single-phase commutator motor has 
been rapid, it would appear unreasonable to look forward to very considerable further 
improvements in those respects where it is still distinctly inferior. On the other 
hand, not only are there also numerous undeveloped features in the continuous-current 
railway motor, but there are other single-phase railway systems where the motors 
driving the train need not, and probably would not, be of the single-phase commutator 
type. One very meritorious and promising system of this kind is that developed 
by the Oerlikon Co., where the motors driving the train are of the continuous- 
current type. In this system, the locomotive carries a single-phase motor, preferably 
of the synchronous type, which drives a continuous-current generator, the voltage of 
which is varied by field control. The speed of the motors driving the locomotive or 
car-axles is thus effectively controlled without the use of rheostats, and regenerative 
braking is exceedingly simple and effective. The continuous-current motors need not 
be located exclusively on the locomotive, but may, in the interests of obtaining a high 
rate of acceleration, be distributed on the trucks of the carriages, thus securing some 
important advantages of the multiple-unit system. In the Oerlikon system, a high 
efficiency during acceleration is obtained, for whatever the rate of acceleration, and 
whatever the current consumed by the driving motors, the current drawn from the line 
is proportional merely to the current consumed by the traction motors plus the internal 
losses in the motor-generator set, and no energy is wasted in rheostats or other controlling 
devices. This system has been illustrated in Figs. 316 and 317, on pp. 351 and 352. 

Wherever alternating current may come to be employed for railway electrification, 
the importance of low periodicity should not be underestimated. It is true that this 
involves still heavier transformers and other control apparatus, but it is also true 
that the chief consideration is the production of a light and efficient motor with high 
power factor, a small diameter, and a reasonably deep air gap. The fulfilment of these 
requirements involves a reduction in the size of the commutator and of the commutator 
losses without sacrifice of good commutating qualities. To reduce the size of the 
commutator and the commutator losses the use of a higher commutator voltage is 
necessary, and this will be the more practicable the lower the frequency. With a lower 
frequency, a good power factor may also be obtained with a deep air gap ; and a smaller 
rotor diameter will be consistent with a good design. 

In the design of the commutatorless induction motor, high rated speed is attended 
with advantages more or less equivalent to those associated with low periodicity. This 
is not the case with the single-phase commutator motor, for the use of a commutator 
involves the necessity of keeping within moderate speeds, if the best results are to be 
secured, and a low frequency becomes all the more important. 

The economic speed of the single-phase commutator motor, while lying consider¬ 
ably below that of the induction motor, will nevertheless be higher than that of the 
continuous-current motor, for the reason that the voltage causing sparking, depends, 
not upon the speed alone, but has a component, which is independent of the speed, 
generally considerably larger than the reactance voltage. 

In Fig. 390 are given comparative curves of efficiency of continuous-current ar d 
single-phase commutator motors, the efficiencies in both cases corresponding to the 
highest speed notch of the controller. The continuous-current motor has only one 
other really efficient position, the full series, and intermediate positions involve 
rheostatic losses. The single-phase motor, on the other hand, has, in virtue of the 
method of regulation by voltage control, a separate efficiency curve with a fairly high 
point of maximum efficiency, corresponding to every controller notch. This is 

416 


Ordinates denote. 













































































































































































































































































































































































. 





















































































■ 



















































































































LOCOMOTIVES AND MOTOR CARRIAGES 


illustrated in Fig. 391, which represents a group of efficiency curves of the same 

Latour-Winter-Eichberg motor for which the efficiency at the highest notch has 
been given in Fig. 390. 

Thus, while the maximum efficiencies of single-phase commutator motors are 
considerably lower than the efficiency of the continuous-current motor on the running 



Fig. 391. Efficiency Curves of Latour-Winter-Eichberg Motor. 


points of the controller, this is partly made up for by the greater number of efficient 
running points in the single-phase system. 

Attention should be drawn to another point, namely, the maximum output of the 
two types of motor. While, as is well known, the output of the continuous-current 
series motor is limited only by the heating, the maximum output attainable by the 
single-phase commutator motor is, for any voltage, sharply defined. A glance at 
the second and fourth vertical columns of Fig. 390 shows that these two repulsion 
E.R.E. 417 EE 



























































































































































































ELECTRIC RAILWAY ENGINEERING 


motors, rated respectively at 60 h.-p. and 175 h.-p., cannot, at the highest voltage, 
carry overloads exceeding 25 per cent, and 15 per cent, respectively, whereas, with 
continuous-current motors for these rated outputs, momentary overloads of 100 per cent, 
and more, occasion no difficulty. When the curves of single-phase motors are plotted 
with amperes as abscissae, as in Fig. 392, this limiting overload is not so clearly 
apparent; it is only evident that the current increases rapidly with decreasing 
speeds. The efficiency curve of Fig. 392 is merely transformed from the corre¬ 
sponding curve of Fig. 390. 

The power factors corresponding to the same four motors are given in the second 
horizontal row of Fig. 390, and from these, together with the efficiency values, the 
curves in the lower horizontal row of Fig. 390 have been prepared, showing the 
volt-amperes required per horse-power developed, by the continuous-current and the 

single-phase systems respec¬ 
tively, when running on the 
highest controller notch. It is 
evident from a study of these 
curves, that for a given voltage, 
the single-phase motor requires, 
on the average, some 20 per 
cent, more current than the con¬ 
tinuous-current motor. Hence 
for a given voltage and outlay 
for copper, the HR loss in all 
apparatus and line will be fully 
40 per cent, higher. While this 
also applies to the Latour- 
Winter-Eichberg system so far 
as relates to the power factor 
at the motors, the system has 
the great advantage over the 
other two systems, that the 
power factor at the generating 
plant will be greater. For while 
some motors will be starting and 



Fig. 392. 


Calculated Cukve oe 175 h.-p. Repulsion 
Motok at 1,500 Volts. 


running at speeds below the point of unity power factor, and thus will be talcing a lagging 
current from the line, other motors will be running above the point of unity power 
factor, and will be taking a leading current from the line. By intelligent operation, the 
lagging and leading currents may largely neutralise one another on a fairly extensive 
system, and thus the generating plant might, under favourable conditions, be designed 
for approximately unity power factor. This is a most important feature, reducing, 
as it may, the capital outlay for the generating plant and the transmission system. 

There is, of course, much to be said on behalf of the single-phase system, but 
since this system has most strenuous advocates, it is not proposed to go into the 
question further than has already been done, since it is believed that, in spite of the 
necessity, in the interests of an intelligent comparison, of calling attention to some 
weak points of the single-phase system heretofore overlooked, its merits have also been 
fairly admitted. It is to be hoped that further progress in the improvement of the 
single-phase motor may lead to the production of a thoroughly satisfactory system for 
the purposes of the electrical operation of main line railways. For dense service, 

418 

































































LOCOMOTIVES AND MOTOR CARRIAGES 

however, there appears to be no sufficient reason to look for the early supersession of 
the continuous-current motor. 

We thus see that the most unsatisfactory aspects of the single-phase system 
relate to the rolling stock equipment. 

The use of high tension continuous current, on the other hand, affords a sound 
engineering basis for railway electrification. On p. 360 allusion was made to proposi¬ 
tions on these lines as laid down by one of us some years ago. Although at that time 
the proposition met with no encouragement, a very considerable revulsion of opinion 
has lately taken place, and the subject of high voltage continuous current railway 
electrification is now beginning to attract the very considerable attention which it 
merits. Under these circumstances the writers have sought and obtained the 
courteous permission to reproduce the article in question. 


The Continuous-current System and the Single-phase System for Traction. 

Many hundreds of thousands of continuous-current railway motors are now in use, 
and are giving excellent satisfaction. The field of operation for electric traction has 
been rapidly extended, and it has encroached heavily upon the suburban and inter- 
urban traffic heretofore handled exclusively by the main steam lines. 

The replacement of steam by electric traction on main lines is still of doubtful 
economic practicability, although much attention has been given to the subject. 

The economic impracticability of operating main lines electrically has related 
chiefly to the difficulty of obtaining any approximation to a uniform load, for, pro¬ 
viding the traditional limit of 650 volts at the train is accepted, the sub-stations 
cannot be many miles apart, and at the customary spacing and speed of through 
trains, a sub-station will be alternately running idle for long intervals and loaded for 
short intervals. Several times more capacity of sub-station apparatus will, therefore, 
be necessary than would be the case could the same amount of work be done at a 
uniform rate. Moreover, the average efficiency is excessively low, owing to the large 
constant losses in such a large installation of lightly loaded machinery. At first 
sight, the natural solution would appear to be to operate by single cars instead of by 
trains. While this would greatly improve the load factor, it would increase by from 
100 per cent, to 200 per cent, the work required to be done per ton hauled a given 
distance 1 at a given speed. This would at any rate be the case at speeds above 
50 miles per hour. Furthermore, there would inevitably be greater danger and 
expense in operating at a schedule speed of 60 miles per hour, six carriages at 5- 
minute intervals, as against one train per half-hour. Were it not for the enormously 
increased friction incurred by single-car operation, this would, however, be the plan 
which would be followed ; and it may, to some extent, indicate the lines on which 
main roads will ultimately be operated. 

An increased permissible voltage w T ould permit of fewer, larger, more uniformly 
loaded, and more economical sub-stations situated at greater distances apart. 

The possibilities in this direction, as associated with the use of continuous- 
current motors, have been but little considered. The hopelessness of the case from 
the standpoint of any such low voltage as 650 has generally led to the expectation 
that some solution by alternating current motors would ultimately be found. A good 

1 Armstrong, “ High Speed Electric Railway Problems,” American Institute Electrical 
Engineers (June 30th, 1903). 


419 


E E 2 


ELECTRIC RAILWAY ENGINEERING 


deal of tentative work with three-phase motors has been carried out during the last 
few years, but the difficulties associated with two insulated conductors, lack of speed 
flexibility, and a number of other disadvantages more or less consequent upon the 
latter, have sufficed to dampen the enthusiasm of many engineers who were originally 
very sanguine along these lines. 

The application of the commutator to the polyphase motor afforded considerable 
promise of giving it greater speed flexibility. Hardly, however, was this appreciated 
before the single-phase commutator motor was brought to a commercial stage of 
development. This naturally concentrated attention upon the problem of the single¬ 
phase operation of main line railways, for the single-phase commutator motor not only 
aftords speed flexibility, but also avoids the necessity for two insulated conductors. 

It is reasonable to base upon these developments, renewed hopes of solving the 
problem of the electrical operation of main lines. Is it, however, reasonable or just 
to the continuous-current motor to disregard its undeveloped possibilities, especially 
in the matter of operation at higher voltage ? Aside from the question of main line 
traction, there is a large field for interurban electric traction and for extensive urban 
and suburban systems. Doubling or trebling the voltage at the train would at once 
immensely extend the range of economic working. There are the further possibilities 
associated with two commutators, or even two motors in series, and treated as a single 
unit. Series-parallel control is well within the range of the practicable at such voltages; 
indeed, the controller problem is, in some respects, simplified by the reduction of the 
current through increased voltage. But in high speed suburban and interurban work, 
with infrequent stops, rheostatic control need detract but slightly from the efficiency, 1 
and as it is for just such work that the higher voltages are desirable, the argument 
would, from the continuous-current motor’s standpoint, be but slightly impaired by 
the assumption of rheostatic control. 

It appears the more desirable to speak on behalf of the continuous-current motor 
in this connection since, contrary to expectations, it is not so much for main line 
work, but more especially for urban, suburban, and interurban work, that the 
single-phase motor is at present being strongly advocated. 

Thus Mr. P. M. Lincoln 2 states:—“Interurban electric traction work is, in my 
opinion, the peculiar field for the alternating current system ” ; also, “ When stops 
are few, and consequently runs are long, . . . the advantage of the alternating 

current system is not so greatly marked. With short runs, on the other hand, and 
consequently frequent starts, . . . the alternating current system can have the 

greater advantage.’’ 

Mr. B. G. Lamrne states:—“ It thus appears that, while suburban work was once 
thought to be the most important field for the single-phase railway, it has now become 
evident that city work, where traffic is very congested in parts of the system, will 
prove to be one of the best fields for this system.” 3 

1 With correctly designed modern motors, the necessary speed variation at constant load may be 
obtained by a rheostat in parallel with the field, and hence efficiently. 

2 Electrical World and Engineer , December 12th, 1903. 

3 In the same article ( Electrical World and Engineer, December 26th, 1903), Mr. Da mm e also 
states:—“ Of course, it is recognised that for heavy railroad service, where all kinds of speeds should 
be obtained economically, the single-phase railway system will undoubtedly show to great advantage 
compared with any known continuous-current system. But, as considerable time will be required to 
equip any railroad service, it is probable that the single-phase railway system will be well tried out 
before there is a good opportunity to give it a thorough trial for heavy work.” 

420 


LOCOMOTIVES AND MOTOR CARRIAGES 

Armstrong and others see the greater possibilities in main line work, and this 
would seem to he the sounder position. 

Inasmuch as superior merits for the crowded traffic conditions of large cities have 
been claimed for the single-phase commutator motor, it is of interest to compare 
the respective features of the continuous-current and the single-phase motor, since for 
crowded city work the former is at present exclusively employed. 

For a given voltage, the single-phase motor has the larger commutator, in order 
to take care of additional parasitic losses. 1 The satisfactoriness of the design of the 
single-phase commutator motor is so dependent upon low voltage, that considerably 
less than 500 volts is advocated for some types, and is probably desirable for all. 
This leads to a further increase in size of commutator, and in the magnitude of the 
commutator losses. The more recent types of single-phase motors have an extra set 
of short-circuited brushes, thus two sets of brushes per pole, as against one set per 
pole for the continuous-current motor. The commutation will not be better than for 
the continuous-current motor. 

The field spools of the alternating current motor have much the higher voltage 
per turn, and a breakdown in the insulation between one turn will occasion heavy 
induced currents in the short-circuited turn, promptly leading to the disablement of 
the motor for the time being. Such a breakdown does not result from the 
short-circuiting of a single field turn in a continuous-current motor. 

The internal losses inherent to the single-phase motor are, according to rated 
capacity, periodicity, speed, and voltage, at least from 15 per cent, to 35 per cent, 
greater than for the equivalent continuous-current designs. 2 Szasz (Zeitschrift fitr 
Elektroteclinik for November 22nd, 1903, pp. 651—653) estimated that the losses in 
the single-phase commutator motor are much in excess of these figures. The motor 
must consequently be larger and heavier or run warmer for a given performance. 
The efficiency is consequently considerably less. It has been pointed out by Szasz 
in the article above referred to, that in the comjiensated type of single-phase motor 
the efficiency falls off badly above and below certain very limited conditions of load 
for given ratios of transformation. This is also evident from Figs. 393 and 394. 
Hence a good deal of intelligence would require to be exercised by the driver 
in operating on the most efficient controller notches for all conditions. Szasz points 
out that the efficiency curve of the continuous-current series motor is far better 
sustained throughout a wide range of conditions. 

1 These, and practically all the disadvantages of the single-phase motor, have been admitted by 
its advocates with commendable frankness. 

2 Lamme states the efficiency of the single-phase motors to be from 1 per cent, to 5 per cent, less 
than that of the continuous-current motor ( Electrical World and Engineer, December 26th, 1908, 
pp. 1048—1046). In this article Lamme gives the following useful summary of the component losses 
in the single-phase commutator motor:— 

(1) Iron loss due to reversals of magnetism in armature and field at the frequency of the supply 
circuit; 

(2) Armature iron loss due to variations in magnetism, dependent upon rotation of the armature ; 

(3) Iron loss in the surface of the field and armature due to the bunching of magnetic lines from 
the teeth of either element ; 

(4) Losses in field windings ; 

(5) Loss in armature windings ; 

(6) Brush losses; 

(7) Friction and windage. 

And on comparing each in turn he shows that, of these seven component losses, only one, the 
fourth, is as low as in the continuous-current motor. 

421 


ELECTRIC RAILWAY ENGINEERING 


The inferiority of the single-phase commutator motor as regards efficiency may be 
seen from Figs. 393 and 394, relating respectively to the Winter-Eichberg 1 motor and the 
Finzi motor. The curves in Fig. 393 are taken from Mr. Eborall’s recent paper 
entitled “ Electric Traction with Alternating Currents.” The full line curves relate to 
the efficiency of the single-phase, and the dotted curve to the efficiency of an equivalent 
continuous-current motor. In Fig. 394 the full line curve represents the efficiency 
of the Finzi motor tested at Milan, and the dotted curve represents the efficiency 
of an equivalent continuous-current motor. The data for Dr. Finzi’s motor are derived 
from Diagrams 1 and 2 of the Electrical Review of November 13th, 1903, ^ ol. 
LIII., p. 769. The continuous-current motor used in this comparison is a standard 


10 













^ - 








1 

Transj 
latio - 


/ Tra 

I 

0 

I 

Ion Ra 

10 * 0 ; 

; 1 



















Broken Line Eft of 125 H.P. cont. current 500 volt Motor 

on Central London Railway. — 

Full Lined - Eft. Curves of Winter-Eichberg 125 H.P. Single- 
__ Phase Motor. 

The curves in this figure have been deiived from the curves 

In Fig. 9 on page 194 of "Electrical Review*' tor 
January 29, 1904 Eboralf*s Paper on "Electric — 
Traction with Alternating Currents "I. 











O 20 40 60 80 100 120 140 160 I8< 

Brttlsh Brake Horse-Power Output. 

Fig. 393. Comparison of Efficiencies of 
Continuous-Current and Single- 
Phase Motors. 


to 

80 

70 

£ 

± 

§ 60 
u« 

•J 

§ 50 

z 

a. 

40 




























■ «• 


✓ 




O Volt* 





[7 / 

// /a 
/ / / 

4 

y 






• I 

j 

/ ^ 
H % 








> 

0 

* 

0 

0 









Broken Line - Eft. of 27 H P. geared cont. current 500 volt 
Motor (See "Elec. Cen6.." figs. 280 and 282, 
p. 251). 

Full Lines - Efficiency Curves of Finzl's Milan Motor at 
80. 100, 120. 140 and 160 Volts See " Electrical 
Review" tor November 13, 1903, Vol. 53, p. 761, 
Diagrams I. and II.) 


O 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 

Brake Horse-Power British) Output. 


Fig. 


394. Comparison of Efficiencies 
Continuous-Current and Single- 
Phase Motors. 


of 


27 h.-p. motor for which efficiency and output curves are given in Figs. 281 and 283 
on p. 276 of “ Electric Machine Design.” 2 

The power factor of the single-phase commutator motor falls considerably short 
of unity for all except a very narrow range of loads. In the case worked out by Mr. 
Lincoln the average power factor at the generators is 0‘85. The power factor during 
acceleration is exceedingly low. 

For the single-phase system considerable auxiliary apparatus is required on the 
car. This consists chiefly of step-down transformer and voltage regulator. Such 
apparatus is heavy and expensive, and introduces further losses. The motors 
themselves are admittedly (Lincoln 3 ) heavier and more expensive. 

In the case worked out by Lincoln, 3 a car equipped with the single-phase system 

1 The motor to which the tests refer was designed by Messrs. Winter and Eichberg. As is well 
known, this type of motor, which has been developed by Latour in France and by Winter and Eichberg 
in Germany during the last few years, has brought the single-phase motor nearer to a distinctly 
commercial stage of practicability for traction and other purposes. 

2 “ Electric Machine Design,” Parshall and Hobart, London, Engineering , 1906. 

3 “ Interurban Electric Traction Systems, Alternating versus Direct Current,” Electrical World 
and Engineer, December 12th, 1903, p. 951. 


422 



















































LOCOMOTIVES AND MOTOR CARRIAGES 

weighed 41*3 tons complete, as against 35 tons for the continuous-current equipment. 
Hie total weight of electrical apparatus carried, is thus in the single-phase system, well 
on towards double the weight in the continuous-current system. This is confirmed by 
Lincoln’s figures, which show over 60 per cent, greater cost per (electrical) car equip¬ 
ment. Sixty per cent, greater cost in such apparatus is associated with a considerably 
higher percentage increase in weight. 

... preparation of a rigid quantitative comparison is, in such a case as this, beset 
with difficulties, but it should be evident from the data set forth, that pending con¬ 
siderable further development, the continuous-current motor has as yet no rival in 
city and suburban work. 

Toi in ter urban work, it is believed that the 600-volt continuous-current motor 
can generally hold its own; nevertheless there appears insufficient reason why 

advantage should not be taken of the higher economies incident to employing higher 
voltage at the motor. ° 

Thus m Lincoln’s comparison of a 60-mile interurban line, 600 volts is taken for 
the continuous-current system, and a cost for the secondary network amounting to 
30 per cent, of the total cost of the electrical system is deduced. In fact, it is only by 
comparing a 3,000-volt secondary network for the single-phase system with a 600-volt 
network for the continuous-current system that an advantage appears to be obtained 
for the single-phase system. 

The following criticisms of Mr. Lincoln’s estimate appear sound :— 

(1) That he overlooks the fact that single-phase generators cost some 30 per cent 
more than polyphase generators for the same rating and guarantees ; 

(y) That he overlooks the increased cost of low periodicity transformers; 

(3) That there is no reason to employ many small and expensive single-phase 
transformers for the polyphase central and sub-stations: it is only in America that 
ns las been customary, and now large polyphase transformers are being substituted 
for groups of single-phase transformers in America also; 

. (4) That the single-phase generating plant is not sufficiently liberally proportioned 
in view of the poor average power factor ; 

(5) That, since the chief handicap of the continuous-current system is, as Mr. 
Lincoln has pointed out, the low tension conducting system, the voltage should have 
been increased, as this is a perfectly sound proposition in the present state of 

the art, much more sound than some of the features of the single-phase system he 
describes ; 

(6) Laige tiansformers are artificially cooled, and some-attendance, such as very 

frequent patrolling, is advisable for the sub-stations, even with the single-phase 
system; b ^ 

(7) The high voltage per turn in the field spools of the alternating current system, 

the less satisfactory commutation, and the more complex auxiliary apparatus will 
inevitably result in a higher percentage depreciation than for the continuous-current 
equipment: nevertheless Mr. Lincoln takes 10 per cent, for the former and 12 per 
cent, for the latter. 1 

Let us compare Lincoln’s 60-mile road, introducing justifiable corrections for his 
single-phase figures, and substituting for his 600-volt continuous-current system, with 
sub-stations, a system with two continuous-current generating systems located 
respectively 15 miles from each end of the system and 30 miles from one another. 
These stations shall be equipped with slow speed 1,350-volt continuous-current 
generators, and the cars shall be fed at an average voltage of 1,300. Bach car shall 

423 


ELECTRIC RAILWAY ENGINEERING 


carry two 650-volt motors connected in series and operated as a 1,300-volt unit. The 

acceleration shall be rheostatic. 1 

The 60-mile road is operated 
on a schedule speed of 30 miles per 
hour, with 30-second stops every 2 
miles. The cars run half an hour 
apart. The braking is at the rate of 
2'0 miles per hour per second (0*89 
metres per second per second), and 
the accelerating is at the rate of TO 
miles per hour per second (0‘45 
metres per second per second). The 
continuous - current car complete 
weighs 36 tons, and the single-phase 
car 41*3 tons. The former carries 
two 150 h.-p. motors, and the latter 
two 165 h.-p. motors. 

The diagram of cyclic operations 
given by Mr. Lincoln for the continuous-current equipment becomes modified, 
owing to rheostatic control, to 
that given in Fig. 395, the average 
input now being 77’5 kilowatts, 
instead of 67‘2 kilowatts, an 
increase of 15 per cent, due to 
rheostatic control. In arriving 
at this figure the weight of car 
is taken at 36 tons, as against 
Mr. Lincoln’s 35 tons, to cover 
the increased rheostatic capacity 
required. Mr. Lincoln’s diagram 
for the single-phase equipment 
is reproduced in Fig. 396, 2 and 
his figure of 73*9 kilowatts average 
input for the single-phase equip¬ 
ment will be employed, except 
that to it must he added the losses in the other apparatus on the car, which, from 
his data, is seen to introduce an increase of 5 per cent. 

Hence the average input per car = 77*5 kilowatts for the single-phase 
equipment. 



Fig. 396. Diagram for Single-Phase 2-Mile Run. 



0 S l-o 1-8 20 29 30 35 4 0 

Minutes 


Fig. 395. Diagram for Continuous-Current 
2-Mile Run. 


1 By merely adding ordinary series-parallel* control apparatus to the equipment of such a car it 
may be run through cities already provided with a 600-volt trolley system, and will give a high 
efficiency even with the number of stops per mile necessary in such crowded traffic. With the single¬ 
phase equipment, on the other hand, such combined service, as pointed out by Lincoln, would lead to 
further serious complications owing to the essentially different conditions introduced by the very low 
voltage of the motors. 

2 From Fig. 396 it is evident that the average power factor during starting is very low, and this 
leads to such large losses due to the wattless component’s I 2 R loss in generators, transformers, line, 
and motors, as to largely offset any gain through avoidance of the use of rheostats in starting. 


424 









































< 

CO 

tb 


Plan Outlines of Motor Carriages 
and Trailers. 




















































































































































































































































































LOCOMOTIVES AND MOTOR CARRIAGES 


Continuous-current Railway 
Average kw. at car in typical 

2-mile run (Fig. 895) . 

Number of cars running at one 

time . 

Number of stations. 

Average number of cars per station 

Average volts at car. 

Average current per car . 

Average current per station 
Resistance of 15 miles of 80-lb. 

track rail and 60-lb. third rail... 
Average line loss per station 
Average kw. per station at cars... 
Average kw. per station at station 

Per cent, loss in third rail. 

Maximum load per station. 


System. 

77'5 kw. 

8 

2 

4 

1,300 volts. 
595 amps. 
288 amps. 

1'13 ohms. 
17'0 kw. 
310 kw. 
327 kw. 
5-2 per cent. 
800 kw. 


(Each power-house requires three 300-kw. generat¬ 
ing sets, of which one is a spare, each gene¬ 
rator built for a guaranteed capacity of 50 per 
cent, overload for 1 hour.) 

Average kw. for whole system ... 654 kw. 


Single-phase Railway System. 


Average real kw. at car in typical 

2-mile run (Fig. 396) . 

Number of cars running at one time 

Number of sub-stations . 

Average number of cars per sub¬ 
station. 

Average apparent kw. per car ... 

Average volts per car . 

Average current per car ... 
Average current per sub-station... 
With sub-stations 12 miles apart, 
80-lb. track rails, and No. 0000 
B. and S. trolley wire, the resist¬ 
ance between sub-stations allow¬ 
ing for increased rail resistance 
Average real kw. per sub-station 
at cars... ... ... ... ... 

Trolley and rail loss per sub¬ 
station . 

Per cent, loss in trolley and rails 
Average real kw. per sub-station 

at sub-station . 

Per cent, loss in step-down trans¬ 
formers . 

Per cent, loss in high tension line 
Per cent, loss in step-up trans¬ 
formers . 

Total percentage loss up to second¬ 
ary distributing system. 

Average real kw. delivered to 
secondary distributing system 
Average real kw. generated at 

power-house. 

Average apparent KW. generated, 

about . 

Maximum load at sub-station (two 
cars starting with, say, 275 

apparent kw. each) . 

(One 350 -kw. transformer will 
take care of this with 57 per 
cent, overload.) 

Average load on sub-station, 

about . 

(These transformers are suffi¬ 
ciently large to take care of 
load if one is cut out.) 
Maximum load on power-house in 

apparent kw., say. 

(Can be taken care of with three 
525 -kw. generators, one for 
spare.) 

(Each generator built for gua¬ 
ranteed capacity of 50 per cent, 
overload for 1 hour.) 

Average real kw. for whole system 
Average apparent kw. for whole 
system. 


77-5 kw. 

8 

5 

1-6 

89-0 

3,000 

29 - 7 amps. 
47 - 5 amps. 


4 - 20 ohms. 

124 kw. 

3 3 kw. 

2‘8 per cent. 

127 kw. 

3 - 5 per cent. 
2'5 per cent. 

3'5 per cent. 

8’5 per cent. 


635 

KW, 

690 

KW, 

810 

KW. 

550 

KW. 


40 per cent. 


1,400 kw. 


690 kw. 
810 kw. 







ELECTRIC RAILWAY ENGINEERING 


Step-up Transformers. 

Three 450-kw. transformers—load 
can be carried by two in case of 
emergency. 


High Tension Line. 

One No. 3 B. and S. gauge line 
each way from power-house 
20,000-volt single phase. 

Maximum loss, about . 8'2 per cent. 

Average loss, about. 2'7 per cent. 

Sub-station Equipment. 

Four sub-stations; the power¬ 
house feeds directly into 3,000- 
volt trolley. 

Each sub-station to contain one 
350- kw. transformer and switch¬ 
board. 


Low Tension Distributing System. 


Entire length of track equipped with 60-lb. con¬ 
ductor rail. 


Entire length of track equipped 
with No. 0000 B. and S. gauge 
trolley. 


Each car equipped with two 150 
h.-p. continuous-current railway 
motors and rheostatic control. 


Car Equipments. 

Each car equipped with two 165 
h.-p. alternating current rail¬ 
way motors with multiple con¬ 
trol apparatus complete. 


ESTIMATED FIRST COST OF ELECTRICAL EQUIPMENT. 



Power 

Station. 


Six 300-kw. 1,350-volt continuous 


Three 525 -kw. 17-cycle single- 


current slow speed generators, at 


phase 3,000-volt generators, at 


£1,200 each. 

... £7,200 

£2,000 each. 

. £6,000 

Switchboards. 

1,000 

Three 450 -kw. 17-cycle 3,000 to 




20,000-volt step-up transformers, 




at £500 . 

1,500 



Exciting generators. 

1,000 



Switchboard . 

760 


£8,200 


£9,260 


High Tension Line. 



Forty-eight miles 1 of 20,000 volts 
single-phase transmission line, 

No. 3 B. and S. gauge conduc¬ 
tors, at £240 per mile . £11,520 

Lightning protection . 400 

£11,920 

1 Another high tension line to be maintained as a spare, at a further cost of some £10,000, ought 
to be provided for the single-phase system, in order to obtain the same immunity from interruption 
of the service which is provided by the continuous-current system. By the use of two power-houses 
in the latter system, the third rail may be divided into four independent sections. With the spare 
high tension line, the advantage for the continuous-current system would thus be considerably greater 
even than that arrived at in the above estimate. 

426 












LOCOMOTIVES AND MOTOR CARRIAGES 

Sub-stations. 

Four 350-kw. 17-cycle 20,000 to 
8,000 volts step-down trans¬ 
formers, at £440 each . 

Five switchboards, at £300 each 
Auxiliary signalling lines for ope¬ 
rating sub-station switches ... 


Low Tension Distribution System. 


Sixty-three miles of 60-lb. conduct¬ 
ing rail, at £500 per mile installed 
Bonding main track—63 miles, at 
£80 per mile. 


i Sixty-three miles, No. 0000 trolley 
£31,500 wire in place, at £180 per mile 
Bonding main track, 63 miles, at 

5,040 £80 per mile. 

Fifteen miles of pole construction, 
not including horse-power lines, 
at £126 per mile . 

£36,540 | 


Twelve continuous - current car 
equipments complete, consist¬ 
ing of motors with rheostatic 
control, heaters, and contact 
shoes, at £1,100 each . 


Car Equipments. 


£13,200 


Twelve alternating current car 
equipments complete, consist¬ 
ing of two 165 h.-p. motors with 
multiple control outfit, heaters, 
and trolley, at £1,700 . 


Total First Cost of Electrical Equipment. 
£57,940 I 


£1,760 

1,500 

1,500 


£4,760 


£11,340 


5,040 


1,890 

£18,270 


£20,400 

£64,610 


Estimate of 

Continuous Current System. 
Eight men at power-houses, two 
shifts, average wage £180 per 

year . 

Fuel, water, oil, etc., at 0 - 30rZ. per 
K\v r .-hour, 4,250,000 kw. -hours 
Repairs and maintenance of power¬ 
house, electrical equipment (4 

per cent, of cost per year) . 

Repairs and maintenance of third 
rail (1 per cent, of cost per 

year) . 

Repairs and maintenance of car 
equipments (12 per cent, of cost 
per year) . 


Total yearly operating expenses ... £10,373 


Alternating Current System. 
Five men at power-house, two 
shifts, average wage £180 per 


year each . £1,800 

Two patrol men, two shifts, 

average wage £180 per year . 720 

Fuel, water, oil, etc., at 0'25^. 

per KW.-hour . 4,600 

Repairs and maintenance of 
power-house, electrical equip¬ 
ment (3 per cent, of cost) . 278 

Repairs and maintenance of high • 
tension line (5 per cent, per 

year) . 596 

Repairs and maintenance of trolley 

(4 per cent, per year) . 730 

Repairs and maintenance of car 
equipment (12 per cent.) . 2,440 


Total yearly operating expenses ... £11,164 


Yearly Operating Expenses. 

£2,880 
5,300 

328 

365 

1,500 


The increased outlay incurred by the use of two power-houses with the consequent slightly increased 
cost of steam plant is largely offset by the saving obtained through dispensing with sub-station 
buildings. In this connection it may be mentioned that Mr. Lincoln makes no allowance for 
depreciation of sub-station plant, and this has not been introduced in the present estimate. 

427 










ELECTRIC RAILWAY ENGINEERING 


The result shows the single-phase system to he 12 per cent, higher in first 
cost, and 7 per cent, higher in operating expenses for the items taken into 
consideration. 

Two power-houses were taken for the continuous-current proposal, as this arrange¬ 
ment is fairly suitable for the line assumed by Mr. Lincoln for his purposes and for 
1,350 volts at the generators. No especial significance is, however, to be attached to 
such choice. For extensive lines, polyphase generation from a single station would 
often be preferable. Moreover, considerably higher continuous-current voltage at the 
generators and motors could have conservatively been proposed with further resulting 
economies, not the least of which would have been the employment of a single power¬ 
house with continuous-current generators for such a case as Mr. Lincoln’s 60-mile 
line. This would have led to lower generating costs, less spare sets, fewer and larger 
units, and a better load factor. 

It is believed that these arguments and comparisons afford ground for the 
opinion that the superiority of the single-phase motor for other than main line 
work is as yet by no means a foregone conclusion. Nevertheless the single-phase 
commutator motor represents a very important advance. It is beyond all comparison 
superior to the commutatorless single-phase motor, and is already not greatly 
inferior to polyphase motors and continuous-current motors. This is an excellent 
record for such a brief developmental period. 

The cost of the 1,350-volt continuous-current system used in the present estimate, 
and that of the 600-volt continuous-current system on which Mr. Lincoln estimated, 
are respectively— 

1,300 volts. 600 volts. 

Total first cost of electrical equipment. £57,900 £75,500 

Total yearly operating expenses for power and 
for maintenance of electrical plant ... ... ... ... £10,400 £11,100 

This shows for the former system an advantage of 30 per cent, in first cost of 
electrical equipment, and of 7 per cent, in total yearly operating expenses for power 
and for maintenance of electrical plant. 

In concluding this chapter we have brought together in Fig. 396a, arranged in 
order of decreasing lengths, examples of eighteen motor carriages used on various railways. 
This has been compiled from the material published by Dawson. 1 In Table CXX. 
we have arranged in tabular form considerable data of interest, which we have 
calculated from the plan outlines of Fig. 396a. 

1 Street Railway Journal , Yol. XXVII., No. 14 (April 7th, 1906). 


428 


LOCOMOTIVES AND MOTOR CARRIAGES 

Table CXX. 


Showing the Seating Capacity per Square Foot of Coaches used on Various Railways. 


Reference 
Number cor¬ 
responding 
to Fig. 

Railway. 

Type of Car. 

Total 
Number 
of Seats. 

Overall 

Length. 

Overall 
Breadth 
(i.e., to 
Outer 
Wall of 
Body). 

Seats 

per 

Square 

Foot. 

Seats 

per 

Foot. 

1 ! 

Illinois Central Railway [ 

Trailer Car . 

100 

71-85 

10-6 

0131 

1-40 


( 

Trailer Car . 

88 

65-0 

106 

0-128 

1-35 

3 

Prussian State Railways . 

Proposed Motor Car . 

73 

61-66 

8-5 

0-14 

1-18 


North Eastern Railway 

3rd Class Trailer Car . 

70 

56-5 

9-0 

0-138 

1-24 

5 J 

J ( 

1st Class Motor Car 

48 

56-5 

90 

0-095 

0-85 

6 ) 

Lancashire and York- f 

Motor Car . 

69 

61-3 

9-86 

0-114 

1-13 

7 j 

shire Railway \ 

Trailer Car . 

66 

60-0 

986 

0-111 

1-10 


I 

3rd Class Trailer . 

64 

58-5 

8-58 

0-127 

1-09 


Mersey Railway, Liver- | 

1st Class Trailer . 

60 

58-5 

8-58 

0-12 

1-02 

1° 

pool 

3rd Class Motor Car . 

50 

59-0 

8-58 

0-099 

0"85 

11 / 

( 

1st Class Motor Car . 

48 

59-0 

8-58 

0-095 

0-81 

12 

Great Northern and City 

Motor Car . 

58 

49-5 

9-33 

0125 

1-17 


Railway 







13 ) 

London U nderground ( 

Trailer. 

52 

50-29 

8-58 

0-120 

1-03 

14 j 

Electric Railway j 

Motor Car . 

48 

50-29 

8-58 

0-111 

0-95 

15 

Manhattan Elevated Rail- 

Motor Car . 

48 

47-08 

8-58 

0-119 

1-02 


way 







16 

Berlin Elevated Railway . 

Trailer 

44 

41-66 

7-42 

0-142 

1-06 

17 

Paris-Lyons Mediter- 

Motor Car . 

36 

40-58 

9-42 

0-092 

0-89 


ranean Railway 







18 

Paris Metropolitan Elec- 

Trailer 

26 

25-57 

7-71 

0-132 

1-02 


trie Railway 








429 





































Chapter X 

TRUCKS 

T RUCKS are either for a rigid wheel base or for bogie stock. In railway practice 
proper, the use of rigid wheel bases may be considered as limited to locomotives, 
since, so far as the authors are aware, there is only one electric railway, the Paris 
Metropolitan, employing motor cars with rigid wheel bases (see Figs. 397 and 398), and 



Fig. 397. Paris-Metropolitan Motor Oar with Rigid Wheel Base. 


these are now being abandoned. From the point of view of truck design, however, it 
is more or less a matter of detail whether the truck is to form part of the under-frame 
of the vehicle itself, as in the case of rigid wheel base stock, or to be merely attached 
to it, as in the case of bogie stock. In either case the truck should be regarded as in 
all respects the equivalent of an electric locomotive so far as relates to general design, 
material, and workmanship, and there is no good reason for relaxing the rigorous 
standards which experience has shown to be necessary in locomotive work. We 
mention this because there is a certain school of engineers and manufacturers who 
appear to regard truck building as an art so distinct from any other branch of 
mechanical engineering, that rough workmanship and inferior material may be 

430 


















TRUCKS 


employed without corresponding disadvantages. The authors not only find no 
justification for this view, but they have found that in truck work, even more than 
in the case of most kinds of machinery, undue reduction of capital cost leads to 
utteih dispioportionate increase in maintenance cost. The writers would further 
contend that if the use of inferior material and workmanship is unjustifiable on 
stationary plant, where a breakdown usually means mere inconvenience and expense, 
it is nothing short of criminal in the case of rolling stock, where a breakdown 
is so very likely to involve injury to life and limb. 

The frames employed on the first electric locomotives of any size—those of the 
Cit} and South London Railway—follow the lines of English steam locomotive practice 
in that the} are built of steel plate riveted up, and with semi-elliptic springs over the 
axle-boxes. Each frame is mounted on four wheels, and carries two motors, the 
aimatures being mounted direct on the axles. This type of frame has been followed 



Fig. 398. Truck of Paris-Metropolitax Motor Car with Rigid Wheel Base. 


with practically no alteration for all the locomotives on this line. The construction 
will be understood from the photograph of Fig. 275, on p. 316. 

The first large electric locomotives in the United States—those of the Baltimore 
and Ohio Railway—follow the locomotive practice of that country, the truck being 
built up of wrought iron bars welded together to form a trussed frame. Each frame 
rests on four wheels, and carries two gearless motors. Two of these four-wheel trucks, 
coupled together, form the under-frame of the locomotive. One-half of the cab, 
together with a sloping end, of the type that has been so widely employed for 
electric locomotives, is carried by each truck. This locomotive has been illustrated 
in Fig. 268, on p. 308. The newer electric locomotives of the Baltimore and Ohio 
Railway (see Figs. 269 to 272, on pp. 310 to 313) also have rigid wheel bases, 
but the frames, which are carried on four axles, are equipped with four geared motors. 
In consequence of the decreased weight of the motor, it became necessary in this later 
type, to increase the weight of the frames in order to secure sufficient adhesion. The 
frames are therefore constructed of cast steel, the side and end members being machine- 
fitted and bolted together. The frame rests on four inverted semi-elliptic springs, the 

431 














ELECTRIC RAILWAY ENGINEERING 


ends of the springs resting on the axle-box tops. The locomotive weighs 73 metric 
tons, and in service two of them are usually coupled together. 

The locomotives now being manufactured for the New York Central Railway are 
of the design already shown in Figs. 252 to 254, on pp. 291 to 294. They have gearless 
motors, and, the necessity for added weight in the frames thus being obviated, a bar 
frame of the American steam locomotive type has been adopted. The locomotive has 
six axles, of which four—the driving axles—carry the frame direct and two through 
pony trucks, that is, two-wheeled swivelling trucks. 

The frame is supported through equalising levers on semi-elliptical springs. The 
equalising lever is practically universal in American locomotive practice, but has been 
comparatively little adopted in this country. Its object, briefly stated, is to enable 
short and therefore cheap and compact springs to do the work of longer ones. Any 



upward movement of the axle relative to the frame will be taken up partly by 
compressing the spring over the axle, partly by raising the frame through the 
lever fulcrum, and partly by compressing the next spring on either side, thus 
reducing the travel of the frame for a given travel of the axle-box. 1 The same 
effect could obviously be obtained by the use of more flexible springs, and this is 
the usual European practice, the springs being made longer and in consequence 
deeper. 

The question of the most suitable material for locomotive frames must depend 
somewhat on whether geared or gearless motors are employed. Where gearless 
motors are used there is no doubt that steel plate or rolled steel sections form 

1 In some steam locomotives an additional use is made of the equalisers, means being provided 
permitting the driver to alter the distribution of the load on the various axles so as to increase the 
adhesion when starting. 


432 







































Fig. 400. Mr. Worsdell’s Design for the Bogies for the Electric Motor Cars for the North-Eastern Railway. General Arrangement 

of Motor Truck (Brush Electrical Engineering Co., Ltd.). 


















































































































































































































































































































































































































































































TRUCKS 

the most suitable material, but if this construction be employed with geared motors 
1 \w often be necessary to ballast the locomotive in order to obtain sufficient 
adhesion. I his has been done in several cases, one important instance in 
this country being the goods locomotives of the North-Eastern Railway. One of 
these locomotives is illustrated in Fig. 399. The under-frame is of rolled steel 
sections, and is ballasted with cast iron blocks. Strictly speaking, the under-frame 
f oes not come within the scope of this chapter, since it is not a truck frame, but 
is itself mounted on two bogie trucks. 

In the great majority of cases arising in electric traction engineering, the motors 
aie mounted on bogie trucks under coaches carrying passengers. 

. M With r< p rd to the desi 8 n of such bogies, the strains they have to carry are 
similar in character to those of trailer bogies, though they are usually greater in 
intensity, more frequently applied, and more irregular. Consequently it would appear 
that, any design generally suitable for a trailer bogie should be suitable for motor 
driving, if due attention is paid to securing the necessary additional strength. The 
type of bogie which is generally used in this country on steam railways, so generally, 



in fact, as to be practically universal, may be described by reference to Fig. 400. It 
has a fiame A of rolled or pressed steel, carried on semi-elliptical springs B, of which 
there is one over each axle-box. The semi-elliptical springs B support the frame at 
lugs C by means of screwed hangers and nuts D. Rubber cushions or short helical 
spiings E aie usually placed between the nuts and the lugs. 1 The axle guards are 
in one piece with the side frame, if this is of pressed steel, otherwise they are of steel 
plate riveted to the frame, as in the case of the bogie shown in Fig. 402 (facing p. 434). 
The transom F (Fig. 400) and the end members are of rolled or pressed steel, riveted 
to the side frames. The bolster H is of pressed steel, or of timber reinforced by steel, 
and is carried by helical springs J on a swing bolster K, hung by links L from the 
transom. This bogie, with various modifications, is in use on almost all steam rail¬ 
ways in this country. Owing, however, to the influence of American practice on 
electric railway engineering, the American type of bogie has been much more 
generally employed for rolling stock equipped with electric motors. The American type 
of bogie, of which an example is shown in Fig. 401, is used, with slight modifications, 

1 The latest bogies on the Great Western Kailway have helical axle-box springs. 

E . R .E. 433 FF 





















































































ELECTRIC RAILWAY ENGINEERING 


for practically all passenger cars on American steam railways. On steam railway 
cars it consists of a timber frame A with cast iron or steel axle guards B—or 
pedestals, as they are called in America—supported by helical springs C on wrought- 
iron equaliser bars D, which in turn rest on the axle-boxes. The transom E and 
bolster F are usually of timber, the bolster resting on elliptical springs carried 
bj 7 a spring plank G, which is suspended by swing hangers H from the transom, the 
hangers being inclined inwards at the top, so that when the car swings outwards in 
passing round curves the inner side of the body is lowered and the outer raised. The 
swing bolster has been in practically universal use, being the standard construction 
adopted in 1884 by the Master Car-builders’ Association. Subsequent to that date, 
however, the majority of car-builders have come round to the conclusion that a rigid 
bolster is preferable, apart from its lower first cost and maintenance. 

It is not purposed to discuss the relative merits of the European and American 
types of bogie. Bolling stock superintendents of steam railways in this country, how¬ 
ever, nearly all of whom have employed both types, are practically unanimous in 
preferring the European type (see Fig. 400), and state that they are much more satis¬ 
factory in service than the American tj-pe, whether built in America or in this country. 
On the other hand, the authors can find no record of the European type having been 
employed for passenger cars in America, although pressed steel trucks (with helical 
springs throughout, however) are largely used for the heavier classes of freight cars. 
It is probable that the type of frame found most satisfactory on each continent is 
largely the result of circumstances. The equalised truck undoubtedly gives slightly 
smoother running on an inferior road, and may be regarded as having been developed 
to meet this condition, since bogie stock came into universal use in America many 
years before it was at all largely used in Europe. On the other hand, on a good road 
there is practically nothing to choose between the two types. The object of equalising 
a bogie is, as in the case of the locomotive frame, simply to make a stiff and therefore 
compact and cheap spring do the work of a more flexible and expensive type. Aity 
upward travel of one axle is taken partly by the nearest, and partly by the furthest, 
spring, this causing less shock to the frame than if one spring carried it all. The 
equivalent of this part of the equalising effect could obviously be obtained merely by 
the use of more flexible helical springs, but it would be difficult to find room for them. 
A further effect of equalising is to increase the periodic time of swing of the frame 
when vertical oscillations are set up, owing to the shortness of the spring base. To 
obtain the same effect with a spring base equal to the wheel base the springs would 
have to be tv'ice as flexible whilst having the same strength. This effect is obtained 
in this country by the use of comparatively long and flexible elliptical springs. 

The built-up bogie of either rolled or pressed steel with elliptical springs is so 
near an approach to the standard locomotive frame in this country, is so largely used, 
and is found to be so generally satisfactory, that it is almost certain to be adopted for 
motor bogies by the majority of those of the railway companies electrifying their lines 
in the course of the next few years. 1 In fact, the North-Eastern Railway, which has 

1 The following is a detailed description of this particular design : “ The bogies are constructed 
of Fox’s pressed steel plates, having four wheels with a 7-foot wheel base. The sole-bars are 
104 x 34 x 4 ins. thick at centre, and 8J x 3j x j ins. thick at ends. The cross-bearers are 
844 x 3| x ^ ins. thick at centre, the bottom flange being sheared from 34 ins. in the centre to 3 ins. 
at the ends. A stiffening plate is also riveted to the web at the centre. The headstocks are 
7f x 3 x ins. thick. The top bolster is 9 ins. X 1 ft. 4j ins. x ^ ins. thick at centre. The 
bottom bolster measures 2 ins. x 1 ft. 04 ins., and is made of oak stiffened by two steel angles, 

434 



_ 12.1 Overall 

10.0 Sote b ar 


'Spring g. 
5 fitHeight free B 
„ loaded 
•TonslOcwL^^ 


5 Spencer /f°j4 ? 
Indihrubber 
concentric Cy/f? 


6 '3"Centres of Jo urnals 


>f Wheels 


30 Wheelbase 


3:0 c.tO c. of Spring 


Whee ls 3'o Dia. 


•^ 6 %" Dia. of Fla 7 « 


Sole bars 
I2'x4 , l2' > 
x3/4° / 


5'.I 'l4. Bolster 


ll'/ 2 ‘t/ei_ iht fr’t 


', loaded ( 
t'U'Tons , 


Elliptic Springs 6plates 3x12 
i _ i Camber free5, 5 /e 0 
loaded 2Tons\33t4 


5.1'U Spring plank 


Heads toe ks 


12 1 Over 


6.3 Centres of Beams 


Fig- 


402. General Arrangement oe 


Motor Bogie in Hay’s Design for the Bogies for the Electric Motor Carriages of the Lancashire and Yorkshire Railway 


























































































































































































































































































































































































































































































































































































































































































































































































































































































































TRUCKS 


in hand one of the largest schemes of this character, has standardised a bogie of this 
type for the purpose. This bogie, which has already been described and illustrated 

(Fig. 400), was designed by Mr. Wilson Worsdell, the locomotive superintendent of 
the line. 

The bogie adopted by the Lancashire and Yorkshire Railway, however, is more or 
less a compromise between the two types. This bogie was designed by Mr. H. A. Hay, 
M.Inst.C.E., and is illustrated in Fig. 402. The side frames a are of deep section 
angle steel, with cast steel stiffeners B and steel plate axle guards C riveted to them. 
The end cross members d are of flat steel bar. The frame is supported by four helical 
springs e resting on the equalisers f. The equalisers are straight, and, instead of 
resting on the axle-box tops, are supported on knife edges on short stretcher pieces g. 
Each stretcher piece rests in a bridle h, which embraces the axle-box and is supported 
on a stiff helical spring J on the top of the box. The bolster K is supported by 
elliptical springs I from the swing bolster in, which is suspended by links n from the 
transom o. There are thus three sets of springs in series between the wheels and the 
body of the coach. In this respect the bogie somewhat resembles the Brill bogie, 
which will be described later on. 

The transom construction in Mr. Hay’s design should be particularly noted; a 
single plate is used to do the work of the top plate and gusset plates. 

It will be noticed that both these bogies (Figs. 400 and 402) have the axle guards 
reinforced by machined steel castings so as to increase the bearing surface of the axle- 
boxes against the jaws. This is usually unnecessary on trailer bogies, but is frequently 
adopted for tender bogies. For motor bogies with axle guards of this type, it is 
indispensable, for although the maximum pressure against the axle guards is no 
greater than on a trailer bogie carrying the same weight, the maximum in either case 
being that due to the thrust when braking, the thrust due to the motor is applied for 
much longer periods than the brakes, and the axle guards will wear very rapidly unless 
thus reinforced. 

In the American equalised bogie as adapted for motors, timber is replaced by 
rolled steel, the frame being usually of flat bar section with the sides and ends in one 
piece and the axle guards of malleable iron or cast steel. There are usually four 

2 x 24 x fins., as shown on the drawing. The centre casting is steel, and the side bearings 
cast iron. A special type of cast-steel axle guide is used, having a bearing surface on the axle-box 
of 63f sq. ins. to compensate for the great pressure which comes on it due to the thrust of the motor 
gearing, and to distribute this pressure uniformly over the journal. The axle-boxes are made of 
cast steel with gunmetal bearings 7f x 4^. ins. wide. A pad lubrication with two spiral springs is 
used. The front portion of the axle-box has wings cast on to support the collector shoe beams. 
The side bearing springs are 4 ft. long, and consist of ten plates, two 34 x f ins., eight 34 x 4 ins. 
The ends are fitted with adjustable hangers and Timmis auxiliary springs, 5 ins. outside diameter and 
2| ins. internal diameter. The bolster springs are composed of two three-coil nests of Timmis unequally 
loaded springs. A teak packing-block, 2f x 12 x 124 ins., is fixed between the bolster and the 
spring-guides plate. The bogies are carried on disc wheels 3 ft. diameter on tread, keyed upon the 
axle. The tyres are 5j ins. wide, and fastened to the wheel centres by retaining rings and eight-set 
screws per wheel. The axles are—6 ft. 6 ins. centres of journals, 8 x 4J ins. journals, 5f ins. 
diameter at wheel and spur-wheel seats. The remaining portion of axle between wheel seats, 
including motor bearings, is 5j ins. diameter. Each bogie is fitted with two G.E. No. 66 motors, 
suspended by two bearings on the axle and a cast-steel bracket riveted on to the cross-bearer. The 
wheels are braked on one side only. The main pull-rod from the Westinghouse horizontal brake 
levers engages with a yoke of the usual type used on tram-cars, and from the ends of this yoke pull 
rods lead alongside the ends of the motors to vertical levers pivoted on a cross-shaft at the ends of 
the bogie upon which the blocks are fixed. The weight of the bogie complete is 8 tons 15 cwts.” 

435 FF 2 


27 § to Top of Ran without Pass. L? 





dej)sfo/e? 


joo/j jfj 




lu oi?igjaisiag^ 


-1 






436 


Fig. 403. General Assembly of Motor Truck for the Motor Carriages of the Manhattan Elevated Railway. 























































































































































































































































































































































































































TRUCKS 


equaliser bars, one each side of the axle guards on each side. The transom is usually 
of rolled channel steel, and the spring plank and holster of suitable rolled or pressed 



steel sections. The transom is usually attached to the side frames by gusset plates at 
the top, and by braces of flat bar at the bottom. The motor truck used on the 
Manhattan Elevated Railway, and shown in Fig. 403, is a typical example of this 

437 




























































































































































































































ELECTRIC RAILWAY ENGINEERING 


form of truck, except that it has a frame of angle section instead of flat bar. Another 
very good example is shown in Fig. 404, illustrating the bogies adopted for some of 



Fig. 405. District Bail way Trailer Truck. 


the later Central London locomotives, which were provided with geared motors, instead 
of the original gearless machines. This bogie, however, has not a swing bolster, as 
the clearance between the train and the tunnel is too small to permit of its use. 



Fig. 406. District Bailway Trailer Truck. 

438 
















TRUCKS 

p. -1 A fUrt Jr ® xa “P le of this type is the trailer bogie adopted for the District 
tail way. This is shown m Fig. 405. The arrangement of axle guards and spring 
pockets in one casting is novel and distinctly good. The steel casting by which the 
name, transom, and braces are connected together is also novel, and ensures a verv 
strong construction. Another type of trailer truck for this road is shown in Fig. 40(3 
and the motor car truck m Fig. 407. The following description of these two trucks’ 
i ustrated in Figs. 406 and 407, is taken from an article by E. E. Cook entitled 

Electnc Traction Trucks,” and published in Traction and Transmission for 
October, 1904 (Vol. X., p. 353) 

“ They are both made mainly of cast steel, with wrought-iron bolsters and 
bolster nousings. The motor truck weighs, without motors or gear wheels, approxi¬ 
mately 10,000 lbs. It is carefully machined in all of its important members: the 
wheels are invariably steel-tyred. The axles are all hollow, having had their 
neutral axis removed. The trucks are made to carry two motors of about 150 h.-p. 
each, with six motors to the train of seven cars. A maximum speed of about 60 
mi es an hour can be attained. The brakes are designed for air-braking, and have to 



Fig. 407. District Kailway Motor Car Truck. 


be much stronger than if used for the ordinary trail truck, for the reasons that there 
is not only an exceedingly heavier load to stop, but there is the momentum of the 
armatures to overcome as well; in fact, the pressure on each brake shoe is at least 
100 per cent, greater than in trail trucks. 

“ The advantages of the use of cast steel are best exemplified in this type of truck 
The design of the side frame shows a very strong heavy trussing, the depth of which 
can be varied to suit the strength required, and if these castings are properly annealed 
there is absolutely no shrinkage strain left in them, so that in this design it is possible 
to get the maximum strength with the minimum weight.” 

Fig. 408 shows the latest type of motor bogie designed by Mr. Parshall for the 
Central London Railway. This combines some of the features of both the steam 
railway car bogie and the electric motor bogie. The frame a is of flat wrought iron 
bar; the axle guards b are double, and are of steel plate, pressed into U shape and 
coming down each side of the top frame. There is only a single equaliser bar c at 
each side, passing between the two side plates of each axle guard. The space between 
the inner and outer plates of each axle guard is filled in with pressed steel distance 
pieces, d, of channel section, cut away on one side to admit the equaliser bar. The axle 

439 












ELECTRIC RAILWAY ENGINEERING 


guard keeps, e, are also of pressed steel of channel section and arranged so that the box 
can be removed by removing a single bolt and dropping the end of the keep. The 
front and rear axle guards are joined by a channel tie bar, f. The transom g, is secured 
to the side frames by gusset plates li, flat bar braces i, and a pressed steel centre piece 
k, of special form, which connects together the transom channels, braces, and bottom 
tie bar. The transom is built of rolled channel steel of standard section, and the 




Fig. 411. Central London Railway : Cast Steel Trailer Bogies. General Arrangement 

of McGuire Truck. 


bolster, l, is of steel plates with interposed distance pieces m. The bolster rests on 
elliptical springs carried by steel plates n, suspended by bolts, o, from the transom 
channels, the height of the spring plate being regulated by the nuts on these bolts, so 
as to keep the car accurately to loading gauge, which is an important point in tube rail¬ 
way work. The transom is provided with angle steel brackets for the noses of the 
motors. Particular care has been taken to avoid the use of bolts except where they 
are absolutely necessary for construction or other reasons, rivets being employed 

440 



























































































































































































































9 6 ' Over frame 


bolts 


\Dia rivets- 


S', D/S rivets 


Dia bolts 


3 2 Centres of Springs 


6'0 Wheel base 


Wheels 2-10 Dia: on tread 


thick 


■*'-? $ Dja rivets^ 


rfPJaS&K.toJvX.-. 


fe 1 Clearance I fu'L 


Plate cut away to suit 
Motor 

on diagonal corners 


[ates on transome L 


Dia bofts 


i 3 to isle t 


8-10 Inside frame 


Cone I in 20 


6 6 Or er 


CZ7/- 


i’dfa rivets with heads p irHy 
& P/attenedin Transome L 


.C r-Tl^ 




U 

j\ 

T~~ 


k s 

i 

•4 

f| 


-4 

a 

•S* 

V. 

to 



c 

-4 

L 

6 

"5 

< 

V 

> 

81 - 

-* 


--I 




rivets 


• r " 


fWHT 

—•-- H-'-i- L- 


-Cl 


W--- 


'Jp Rubbing plate on ; -» 

^Transome C, 9$ -6j 


c £ os re. 


/ Dia Suspension bolt$ 


4 4 Centre ot 


Sprjngs 


o'2 Centres Of Beams 8. Journals 


4flj Gauge 


Load on each bolster spring (Two) 5 Tons 
Lead on each equalizer spring (Pour) 3j> Tons 


Fig. -108. Central London Railway : General Arrangement of Motor Bogie. 


210 Dia on tread 






















































































































































































































































































































































































































































































































































































































































































































































































































































Fig. 409. Hedley’s Heavy Service Motor Truck used at Chicago. 


































































































































































































































































































































































































































































m 


410. Cast Steel Tkaileb Teuck. 

































































































































































































































































































































































si 

s 


412. J. G. Brill Company No. 27 E Truck por Brooklyn Heights Elevated Bailway. (May 22nd, 1901.) 





















































































































































































































































































































































TRUCKS 


wherever it is possible to do so. The brake foundation work on this bogie is of a special 
type, as the brake pull rod is unusually low down, owing to the under-frame of the coach 
being only 14 ins. above the rail level. The bogie centre is of cast steel, the lower 
part being so constructed as to contain a large supply of lubricants. 

Soft cast steel has been largely employed for frames, especially in Chicago, where 
it seems to be a material particularly favoured both by manufacturer and by railway 
engineer. The material has given excellent service. One of the best known and most 
satisfactory frames of this type is that designed by Mr. Hedley for an elevated railway 
in Chicago. A motor bogie of this type is shown in Fig. 409. The motor bogie 
adopted by the Underground Electric Railways Co. of London for the Metropolitan 
District Railway (Fig. 407) is very similar to this. A trailer bogie of cast steel is 
shown in Fig. 410. A certain number of cast steel bogies have also been used on the 
Central London Railway, and have given very good results in low cost of maintenance 



Fig. 413. Brill Truck. 

and in freedom from breakdowns ; in these bogies the transoms and bolsters as well as 
the frames are of cast steel. Fig. 411 shows the general arrangement of these bogies. 

The Brill bogie, to which allusion has already been made, hardly corresponds 
with either the European or American type. A typical Brill bogie is shown in 
Fig. 412. Each side frame, a, consists of a single piece, forged under hydraulic 
pressure, with jaws for the axle-boxes similar to those in an American locomotive 
frame. The end members, b, of the frame are of rolled angle steel. The frame is 
carried by helical springs, c, resting on the axle-boxes. The bolster, d, rests on elliptical 
springs e, but the swing beam/, on which these are supported, instead of being hung 
on swing links, is carried by two beams, g, which practically act as ecjualiseis, and 
which are supported by means of helical springs, h, carried in stirrups, k, hung from 
the top frame and free to swing sideways. In this way exceptionally easy riding is 
obtained, there being three sets of springs in series. Photographs of Brill trucks are 
shown in Figs. 413 and 414. 

Both cast steel and forged frames have an advantage in reducing the number of 
parts as compared with built-up frames. Solid and built-up frames have each, 

44 1 







ELECTRIC RAILWAY ENGINEERING 


however, their own disadvantages. There must always he some uncertainty as to the 
internal condition of castings, and if a cast steel frame does break, it is liable to do so 
with much less warning than a forged or built-up frame. The forged frame is, 
undoubtedly, extremely good if great care be taken that the material is never worked 
below a proper heat. This, however, is difficult to ensure, and the forgings are 
sufficiently complex in shape to impose great initial strains on the metal if worked too 
cold. The built-up frame is free from these uncertainties as far as the individual 
parts are concerned, and in view of the almost universal employment of built-up plate 
frames for locomotives, except in America, it cannot seriously be urged that the number 
of riveted parts renders the frame unreliable. It is usually claimed by the advocates 
of cast steel that it is very much cheaper than either built-up or forged frames. The 
authors’ experience, however, hardly bears out the claim. In this connection it may 



Fig. 414. Brill Truck. 

be of interest to note that the price paid for the cast steel bogies in use on the Central 
London Railway was almost exactly the same as that paid for the new standard bogie 
of Fig. 415. The number required in each case was small, but as the cast steel truck 
was fairly near the maker’s standard, whereas the other was an entirely new design, 
the claim of cheapness hardly seems to be sustained. Quotations for another type of 
motor bogie in use on the same railway, and resembling the Manhattan motor-bogie, 
were also almost exactly the same figure. 

On the whole, the authors prefer a built-up frame to either of the other two types, 
and it will be seen from the examples given that the majority of railway engineers in 
this country are of the same opinion. 

With regard to the details of the frame design, a weak spot found in several 
designs is the part of the frame between the jaws of the axle guards. With inner- 
hung brakes and a frame either equalised or having springs immediately on the axle- 
boxes, the stresses at this point are small, and are practically limited to those due to 

442 








Fig. 415 . Bogie Truck under Trailer End of Central London Railway Carriage. 


K - ei * 










































































































































































































































































































































♦ 





TRUCKS 

the forward or backward thrust of the axle. With outside-hung brakes, however and 
vrth elliptical springs over the axle-boxes, or with two helical sprinos one elch i’de o 

f™r ai to% d 1 6 St ‘' e8S :, S 7 ° bVi0USly ^ ; ™> * « » nof uncoZon, how. 
, to find bogies with these arrangements, and with frames having light ton 

members properly braced so as to form a truss between the axle guards and the 

fronMhe It "f T", ' ,a ' VS ° f the ^ gUards ’ where the bendin 8 moment, apart 
thrTin the I °, he t « ak f ’ 16 qUite 8 quarter or even as much as a third of 

exot T Pa t ’ t le frame C ° nSistS 0f the toP member only, without reinforcing 

xcept for such support as is given by the axle guard keep. The result is that the axle 

guards spiead at the lower end of the jaws, and in some cases cracks start upwards and 
outwards from the corners of the jaws. 1 

Another fault sometimes found is the indiscriminate use of bolts instead of 
wml t m tluck construction. This, however, is not a common fault in English 
woik. Some manufacturers maintain that a fitted bolt is better than a rivet in 
? n ny ° aS ®; ThlS f lai “’ however, can hardly be sustained in face of the fact that 
a 1 other constructional work experience has led to the universal use of rivets 
o ts only being allowed in special cases where riveting is impossible. Under the 
constant vibration to which bogies are subjected, bolts are even more objectionable 
lan m ordinary constructional work, requiring constant attention to ensure that 
the nuts do not jar loose. Bolts should never be employed where rivets can be 
used, except for parts that must in the ordinary course be removed periodically for 
renewals. It is, of course,_ necessary that the riveting should be properly done, but 
m the authors experience it is much more difficult to ensure good fitting bolts than 

The car body is usually connected to the bolster of the bogie by means of male and 
female centre bearings M and N (see Fig. 400, facing p. 482), preferably of cast steel, 
rubbing plates 0 being provided near the ends of the bolster and the car body bolster 
so as to prevent the car body from rolling. In order to allow the bogie to swivel 
leely, the usual practice is to allow a slight clearance between the upper and 
lower side rubbing plates, so that normally the whole load is carried on the centre 
bearing. Under these conditions the pressure should not exceed 400 lbs. per 
square inch on the bearing. . It is of particular importance that the pressure be 
kept low, since the centre bearing is required to be constantly starting from a state 
of rest, and, as Thurston has shown, the coefficient of friction, under this condition, 
increases as the cube root of the pressure, whereas with a lubricated journal 
when running, it diminishes with an increase of pressure. Both centre and side 
bearings should preferably be constructed so as to contain a supply of lubricant, and 
for this reason the female centre is usually on the bogie and the male centre on 
the under-frame of the car body. 

It is of very great importance to secure easy swivelling of the bogie under the car 
body, and this will usually require more attention in the case of motor than in that of 
tiailei bogies. With motor bogies there is, in the first place, much greater difficulty in 
swivelling owing to the increased load on the centre and side bearings—motor coaches 
being of necessity heavier than trailer coaches for similar service—and, in the second 
place, much more serious results follow from insufficient swivelling. There can be no 
doubt that by far the greatest part of the wear on rails and wheel flanges on curves is 
due to the grinding of the outer leading wheel against the outer rail caused by the 
incoiiect position of the bogie relative to the rails. Where the coach is subjected to 
puli only, as in the case of a steam train, the pull of the couplings will tend to lessen 

443 


ELECTRIC RAILWAY ENGINEERING 


this effect, but if the coach is being pushed, the effect will be greatly increased, and 
on a motor-driven bogie it becomes a very serious matter. With the ordinary side 
rubbing plates, even if they are adjusted so that when the car is stationary the whole 
weight of the body rests on the centre bearing, it will be found that on curves where 
the conditions as to speed and radius are at all severe the pressure on the outer bear¬ 
ing will be so high that the bogie will not swivel without great difficulty, the difficulty 
being naturally greatest on the sharpest curves, that is at the very place where it is 
most required to swivel easily. As far as steam railways are concerned, the general 
consensus of opinion of authorities on rolling stock appears to be that the ordinary 
type of centre plate and side rubbing plate is good enough and has advantages in 
points of simplicity over any special devices. For electric railway conditions it may be 
worth while in many cases to employ ball bearings for the centre plates and rollers for 
the side bearings, the additional expense being more than offset by the saving in wear 
of wheels and rails and the reduced strains in the bogie frame. The practice of 
having the car body carried on the side bearings instead of on the centre bearing 
is advocated by a considerable number of railway engineers. Car bodies so 
mounted roll less than with the more usual arrangement, which is a very important 
consideration in tube railway working. If this practice be adopted it will be found 
almost imperative to employ ball or roller bearings. A pin termed a king pin 
or centre pin is usually passed through a central hole in the centre bearings. 
The necessity for this in ordinary running is not very obvious, but in case of 
derailment it may serve to keep the bogie in place under a shock that would unseat 
the centre bearing. 

We may now pass on to the consideration of details which apply to either rigid 
or bogie trucks. Of these details we may conveniently consider first the springs. 
Semi-elliptical springs for locomotives are usually designed in accordance with the 
following formulae, due to D. K. Clark : 

span of spring in inches, 
breadth of plate in inches, 
thickness of plate in sixteenths of an inch, 
number of plates. 

deflection in inches per ton of load, 
safe load on spring in tons. 

BT 2 N 
11-3 S' 

11-3 S L 
B T 2 ’ 

0T4 S 3 
T 3 B N’ 


Let S = 
B = 
T = 
N = 
D = 
L = 

L = 
N = 
D = 


In modern practice the coefficient of 1T3 is regarded as somewhat small, and a 
figure of 14 or even 15 is employed. Taking a coefficient of 14 in these formulae, 

O'Ol S 2 

gives a normal safe deflection when fully loaded and at rest of —^—. 

A complete elliptical spring can, of course, be treated simply as two semi-elliptics 
in series, the maximum safe load being the same as for the semi-elliptic, while the 
deflection produced by the load will be double. 

444 






TRUCKS 


For helical springs, Rankin gives the following formulas: 

Let R = mean radius in inches. 

cl = diameter of spring steel in inches. 
b = width of spring steel (square) in inches. 

N = number of coils. 

D = deflection in inches per ton of load. 

G = coefficient of transverse elasticity (about one-third of the modulus 
of elasticity, or about 5,000 tons). 

F = maximum safe shearing stress. 

L = maximum safe steady load (say about 15 tons). 

D = 64NR3 = 0 . 018 N R 3 


G d i 


d i 
d 3 


w - °' 196 F d 3 _ n w . , , 

vv -^- — 2 — — approximately. 

This gives a maximum safe deflection at rest of 

12-57 NFR 3 _ 0-0877 N R 2 


G d 


d 


With square section steel these figures become— 

12 N R 3 _ 0-0075 N R 3 
G 5 1 • 


D = 


W = 4-74 

R 


Maximum safe deflection at rest = Q 035 N R 2 


The arrangement of brake foundation work is a matter that vitally affects the 
questions of maintenance and safe running, especially when the speed is high in 
relation to the frequency of stops. 

The main points to be borne in mind in designing brake work are— 

(1) It must be equalised; that is, the pressure on the wheels must be equal (or 
adjusted to the loads on the wheels). 

(2) The blocks must be hung so as to wear evenly over their whole surface. 

(3) The blocks must cleai the wheels properly under all conditions except when 
brakes are set. 

(4) Means must be provided for quickly and readily taking up ware till the brake 
blocks are reduced to the minimum thickness which is considered safe. 

(5) The blocks must be readily removable for renewals. 

On ligid wheel base rolling stock it is usual to employ brake blocks on each side 
of the wheel, and this piactice is a very desirable one where it does not involve too 
much crowding up of the brake foundation work, as it avoids the severe stresses on 
the axles caused by pressure on one side only. 1 It does not, of course, avoid the 
much smaller side thiust due to the fact that the retarding action of the wheels is 
transmitted through the axles. 

On bogies, however, and especially motor bogies under cars, it is often difficult 
to accommodate the foundation work required for double brake blocks and still more 


1 Tlie resultant of the brake-block pressure and the load may amount to 40 per cent, more than 
the load alone. 


445 










ELECTRIC RAILWAY ENGINEERING 


difficult to give enough access to the foundation work to ensure its proper inspection 
and easy adjustment, and single blocks are consequently more common. 

The question, then, that has to be settled, is that of the relative advantages of 
inside-hung and outside-hung brake blocks, that is, whether the blocks are to be 
between the wheels, as in Fig. 408, or outside them, as in Fig. 410. On American 
steam railways, outside-hung brakes are almost exclusively employed, both on goods 
and passenger stock, and where this arrangement is not prevented by other conditions, 
it should always be adopted, the reduction in maintenance cost due to the easy access 
to the brake work being sufficient to outweigh all other considerations. The outside- 
hung brake, however, has the disadvantage that when applied it pulls down one end 
of the bogie frame and pushes up the other, thus subjecting the bogie frame to stresses 
which it need not otherwise carry, and increasing the load on the journals. This is 
particularly noticeable in the case of equalised bogies. Normally there is no vertical 
bending moment in the frame except between the points of support, i.e., the equaliser 
spring pockets. When brakes are applied, however, a considerable load is applied at 
the end of the frame, that is practically at the end of a cantilever supported at the 
spring pocket, and it is obvious that the frame must be considerably stiffened to carry 
this. It will be noticed that in Fig. 405 this is done by a strut from the bottom of 
the axle guard to the corner of the frame. The downward pull at the leading end is 
also liable to bring the top of the axle guards down hard on to the equaliser on the 
top of the axle-box, thus producing the unpleasant jarring frequently felt in rolling 
stock with equalised bogies when brakes are applied. An attempt has been made to 
overcome this in the so-called “ non-tilting ” frame, which is an equalised frame 
with additional helical springs over each box. It is obvious, however, that the 
equalisation must diminish as the non-tilting properties are improved. 

On bogies other than those of the equalised type the disadvantages of the outside- 
hung brake are much reduced, since, the frame being supported directly over the axle, 
the vertical bending moment at the point of support due to the brake block pull is 
about halved. 

The American type of brake foundation for steam railway passenger stock is well 
illustrated in the cast steel trailer bogie shown in Fig. 410. The brake blocks A are 
carried in steel castings B (brake heads), each pair of brake heads being coupled by a 
brake beam C, and suspended from the frame by the brake hangers D. Safety 
hangers E are also provided to support the brake beams in the event of a hanger 
breaking, and release springs F to hold the brake blocks off the wheels. In some 
instances the release spring also acts as a safety hanger. The angle of the brake 
beams can be adjusted by means of a turnbuckle G, so as to ensure the correct position 
of the brake blocks as they wear out. The pull rod H on the car body is attached to 
the upper end of the live lever I, which is at the outer end of the bogie, and is attached 
near its lower end to the brake beam. The lower end of this lever is connected to the 
lower end of the dead lever J by means of the brake rod K. The dead lever is attached 
near its lower end to the brake beam at the inner end of the bogie, and at its upper end 
to a fulcrum on the bogie frame, which is adjustable to take up the wear of the blocks. 
In the brake foundation of Fig. 410 a further adjustment can be made, the relative 
positions of J and K being adjusted by the set screw L. 

This arrangement is not usually a suitable one for motor bogies, owing to the 
difficulty of finding room for the beams and the lower brake rod on account of the 
collecting gear and motors, and the usual plan is to dispense with beams and have a 
live and dead lever and pull-rod on each side of the bogie, the motion of the car body 

446 


TRUCKS 

pull-rod being communicated to the live levers through the two upper pull-rods 
connected by a yoke at the inner end of the bogie. The yoke is in the form of an arc 
of a circle struck with the bogie centre as its centre, so as to allow the bogie to swing 
without altering the setting of the brakes. This arrangement is illustrated by the 
North-Eastern and the cast steel motor bogie shown in Figs. 400 and 409 respectively. 

When inside-hung brakes are employed, whether with or without beams, the 
individual details are quite similar to those for outside-hung brakes ; the only 
differences aie in the arrangement, the live lever being near the inner end and the 
dead lever nearer the outer end of the bogie, and the lower brake rod being in thrust 



Fig. 416. Motor Truck showing Arrangement op Brakes on Manhattan Railway. 


instead of in tension. A suitable arrangement with beams is shown in the trailer 
bogie in use on the Central London Railway (Fig. 415), and the corresponding 
arrangement without beam in the Manhattan Elevated motor bogie (Fig. 416). As 
has already been stated, the Central London motor bogie brake gear (Fig. 408) is 
somewhat unusual in its arrangement owing to the small height of the pull-rod on 
the car body. In general it may be described as an inner-hung brake foundation 
turned upside down, the dead lever fulcrums being at the lower end of the levers 
and the brake rod at the upper end ; there being no convenient method of supporting 
a yoke for connecting to the car body pull-rod, it is replaced by a beam suspended by 
hangers from the end of the bogie frame. 


447 
























































































































































ELECTRIC RAILWAY ENGINEERING 


With regard to the pressure to be employed on the blocks, the usual practice is 
to make the maximum pressure of the brake block 80 per cent, of the wheel load of 
the empty car. This gives the maximum effort that can safely be applied without 
skidding in the case of trailing wheels. The same rule is sometimes applied in the 
case of driving wdieels. This, however, ignores the kinetic energy of the armatures, 
which frequently amounts to 10 per cent, of the kinetic energy of the moving load and 
of wheel rotation combined. 1 The kinetic energy of the armature would enable higher 
pressure to be used without skidding the wheels, and a safe rule to take would 
probably be 80 per cent, of the wheel load for trailing and 90 per cent, to 95 per cent, 
for driving wdieels. It is, of course, necessary to consider carefully the variation in 
load between loaded and empty cars. As a rule this is not a serious consideration for 
heavy railway work, the variation seldom exceeding some 10 per cent. If it exceeds 
this figure, however, it wdll be necessary to increase the braking effort even at the risk 



of skidding a lightly loaded car, in order to obtain adequate retardation when it is 
fully loaded. If the variation is 20 per cent., it would probably be advisable to 
increase the figures given above by another 10 per cent. Such a variation as this, 
however, would correspond more nearly to the condition of trailing wheels, or of 
tramcar driving wheels. 

ihe standard English type of brake block is a single casting attached direct to the 
levels. In America, however, the brake block—or shoe, as it is termed—is of simpler 
foim, and is carried in a cast steel brake head, which in turn is attached to the levers. 
Ibis arrangement certainly presents considerable advantages when braking is severe, 
and cars have to be frequently reblocked, since the wearing parts are cheaper and are 
more quickly replaced. Consequently this arrangement has been adopted in this 

On the Central London Railway it is 13 per cent, of the moving load on the motor bogie, and 
02 per cent, of the total moving load of the train. 

448 







































































TRUCKS 


country by certain railways where the schedule speed is high in consideration of the 
fiequency of the stops. The brake heads and shoes adopted for the District Railway 
are the standards of the American Master Gar-builders’ Association, and are shown in 
Figs. 417 to 419. There are two slotted lugs on the bead and one on the shoe. The 
lug on the shoe A comes between those on the head B, and a curved tapered key 
of rectangular section is passed through the slots and rests between two lugs at the 
top and two at the bottom of the head, thus securing the shoe. This pattern is very 



Pig. 420. Fig. 421. 

Figs. 420, 421. Central London Railway: New Brake Block for Motor Trucks. 


satisfactory where the brake shoes are readily accessible, as is usually the case with 
outside-hung brakes. On cars where the framing comes down over the bogie, how¬ 
ever, it is found to be very inconvenient, owing to the difficulty of removing the key. 
These conditions occur both on the motor and on the trailer bogies on the Central 
London Railway, and to meet them the form of head shown in Figs. 420 and 421 was 
adopted. The shoe is provided with a longitudinal rib on the back, which fits loosely 
into a corresponding groove in the head. The shoe also has a lip which hooks over 
the upper end of the head, resting between two lugs on the head, which prevent 
E.R.E. 449 G G 


































































ELECTRIC RAILWAY ENGINEERING 


movement sideways. At the lower end there is a lug on the head, which fits loosely 
between two lugs on the shoe, a pin being then passed through holes in the lugs. The 
whole arrangement can also be seen in Fig. 408. To remove a shoe, all that has to 
be done is to remove this pin and raise the shoe about three-eighths of an inch. This 
arrangement works quite satisfactorily, and enables trains to be reblocked in a 
remarkably short time. 

Both the Lancashire and Yorkshire and the North-Eastern Railways adhere to 
the standard English practice of attaching the brake block direct to the levers, but, the 
stops being much less frequent on these lines, it is probable that blocks will not have 
to be renewed so often as on lines of the Central London or District Railway type. 
Considerable difference of opinion exists as to whether it is desirable or otherwise that 
the brake shoes should engage the flange or only the tread of the wheel. On steam 
locomotives the blocks engage the flanges in most cases, and in America, but 
never in this country, on the coaches also. On motor bogies it is almost universal in 
America for the blocks to engage the flanges, and it is also very common practice in 
this country. Instances of the blocks engaging the flanges are the motor bogies on the 
North-Eastern Railway (Fig. 400) and the cast steel bogie of Fig. 409, whilst the 
alternative is adopted on the Central London (Fig. 408), the Lancashire and Yorkshire 
(Fig. 402), and the cast steel trailer bogie (Fig. 410). Where braking conditions 
are severe, the w r ear of the block on the back of the flange has been found objectionable 
with the English section of tyre, as, owing to the back of the flange being vertical for 
more than half its depth, it is impossible to correct this when turning up the wheels. 
This effect is increased b} 7 the tendency of the blocks to travel outwards when the 
brakes are applied, owing to the coning of the wheels. In more than one instance, 
the grooved type of block has been abandoned for this reason. With the American 
section of tyre, however, the back of the flange being curved throughout its whole 
depth, the true section of the flange can always be restored by turning. For this 
country, therefore, the authors are of opinion that the plain block bearing only on the 
tread of the wheel is decidedly preferable, especially where braking is severe. When 
the blocks bear only on the tread it becomes necessary to provide some means for 
preventing them from travelling outwards owing to the coning of the wheels. Where 
brake beams are emploj^ed these will be sufficient; where they are not used the levers 
on opposite sides of the bogie should be tied by a cross-bar, as in the case of the 
Central London and Lancashire and Yorkshire Railways. The extensive use of 
grooved blocks on locomotive and on motor-driven wheels is probably due more to the 
difficulty of finding room for such cross-bars than to any inherent advantages of the 
grooved block. The brake blocks should preferably be of cold blast cast iron, unless 
some one of the several patent brake blocks on the market is used. Some of these patent 
brake blocks give very good results. Brake heads should be of soft cast steel. Pull- 
rods should preferably be of hammered scrap iron, though there is not much to choose 
between this and the best qualities of iron bar. Levers and hangers should be of the 
best quality wrought iron, fixed brackets of wrought iron or mild steel. In America 
the beams are frequently of timber, sometimes braced with wrought iron bars; it is, 
of course, an advantage to have all parts of the brake foundation as light as possible 
in Older to secure quick application, but, in the writers’ opinion, if special lightness is 
desiied, a steel tube truss is a more logical arrangement where the bogie is otherwise 
of metal tlnoughout. In the great majority of cases, however, a flat wrought iron or 
mild steel bar is perfectly satisfactory for brake-beams. Holes for pins in brake 
iigging should be drilled (never punched) in. slack for the pins, and both holes and 

450 



Central London Railway: Carriage Axle- 13 ox. 


































































































































































































































































































































































































TRUCKS 

pins should be case-hardened. To reduce the number of spare parts it is very desirable 
to use one size of pin throughout, say 1* ins., the holes being 1$ ins. Pins are best 
secured by means of split pms with washers under them; the washer is an essential 
P a it ° f . fche arrangement. Safety hangers and brackets should be used with discretion • 
a certain number of such precautions are no doubt advisable, but in brake work, as in 
most other such matters, it is better to make a sound job of the actual work than to add 
numerous safety devices, and it not infrequently happens that more trouble is given by 
the hangers than by the brake foundation proper. 

The method of attaching the motors to the bogie is a matter of prime importance. 

Generally speaking, the most satisfactory plan is the usual one of placing the motors 

between the axles and supporting each motor on one side by bearings on the axle so 

as to keep the gear properly meshed, and on the other by a spring support attached 

to the bogie frame. In the case of a heavy motor there is usually a nose in the frame 

casting which rests, on a bar carried by springs on the transom. The authors are 

inclined to lay considerable stress on the spring support; its effect on the permanent 

way or the coach body is not very important, since, in any case, there will be a 

set of springs between each of these and the motor; but in more than one case it has 

been found that where the nose rests on a rigid bracket both the nose and bracket 

wear very rapidly, owing to the fact that, as the motor bearings follow the movement 

of the axle relative to the frame, the nose is drawn to and fro along the supporting 

bracket Similar effects may be produced by side play between the axle-boxes and axle 

guards, by end play of the motor on the axle, and by lateral bending in the borne 

„f' howev f ’ the nose of tbe wotor is damped to a yielding spring support, the 

effects will be much reduced. 

This method of suspending the motor has, of course, the effect of putting 
from 50 to 60 per cent, of its weight direct on the axle, which generally means 
increasing the non-spring-borne load at least 100 per cent., and occasionally applying 
shocks to the axle equal to several times the weight of the motor, when the axle 
suddenly moves or stops, moving relatively to the bogie frame. Consequently 
numerous attempts have been made from time to time to modify the arrangement 
so as to take the weight of the motor entirely off the axle. The defect of all such 
devices with which the authors are acquainted, however, is that, as the motor must 
be centred on the axle on account of tbe gear, it will still have to move with the 
axle, so that the conditions for a horizontal movement are unchanged, whilst for 
a sudden vertical movement all that can be done is to convert a rotation about 
the nose into a rotation about the centre of gravity. The effect of this in almost 
every case is to increase instead of to decrease the shocks to which the axle is 
subject. To explain this, we may assume, with a close enough approximation to 
accuracy, that the motor is a uniform cylinder with its centre of gravity in the 
axis of the aimature shaft, and that the centre of the nose suspension and the 
axle suspension are at the periphery, at opposite ends of a horizontal diameter. 
The radius of gyration of the motor rotating about the armature shaft will then 

be -yg of the distance from the axis of the armature" shaft to the nose suspension 

or to the axis of the driving axle. For a given vertical movement of the axle, 
therefore, the corresponding average travel, and therefore the acceleration of the 

motor, will be — with nose suspension, and - with centre of gravity suspension. 

The leverage of the axle in the two cases will obviously be in the same ratio, so that 

45 i G G 2 



ELECTRIC RAILWAY ENGINEERING 


the force required to be exerted by—that is, the blow to—the axle will be in the 

ratio of ^ ^ ) to ^ ^ . The shock to the axle will therefore be twdce as great 

with centre of gravity suspension as with nose suspension. Of course with centre 
of gravity suspension the blow to the axle will be the same for upward or downward 
travel of the axle, whereas with nose suspension the total load will be increased by the 
weight of the motor on the axle for upward movement and decreased by it for down¬ 
ward movement, so that up to the point where the movement is sufficiently rapid to 
make the blow greater than the weight of the motor the advantage is with the centre 
of gravity suspension. Such blows as these, however, are too small for consideration 
compared with blows of several times the weight of the motor, which must occur at 
frequent intervals, and then the advantage obviously lies on the side of the nose 
suspension. For instance, if with a certain vertical movement of the axle in a certain 
time the force applied at the axle with centre of gravity suspension is six times 
the weight of the motor, the corresponding force with nose suspension -would be three 
and a half times the weight of the motor for an upward movement (half its weight 
being on the axle), and two and a half for a downward movement. 

If, on the other hand, the suspension be moved further away from the axle than 
the outside of the motor case, the travel of the motor for a given vertical travel of the 
axle will again be increased, so that it appears that the ordinary nose suspension 
approximates very closely to the most theoretically favourable one, as far as blows 
to both motor and axle are concerned, while, even if it were not theoretically the best 
point of suspension, the simplicity of the arrangement would give it a great advantage 
over any other system. 

The proper position of the motors is obviously between the axles as far as good 
running of the bogie is concerned. In certain cases, however, where the construction 
of the cars renders it necessary to have the bogie between the side sills, it may be 
necessary to so reduce the wheel base in order to allow the bogie to swivel sufficiently 
that there is no room for the motors between the axles. This requires placing the 
motors outside of the axles, but this arrangement should never be employed where 
it is possible to avoid it, since, owing to the vertical and transverse horizontal oscilla¬ 
tions due to the short wheel base and great overhanging loads on the ends, the bogie 
will hardly ever rise really well at anything above moderate speeds. In the first 
experimental motor cars used on the Central London Railway, which were converted 
from trailer cars, the bogie had to swing between the sills, which came just at the 
most inconvenient height, i.e., opposite the axle-boxes. It was thought preferable, 
however, to use bogies with inside-hung motors, although it necessitated using very 
short journals, the actual size of the journals on these bogies being 6 ins. X 4 ins. In 
the motor car finally adopted, the design of the under-frame was modified to get over 
this difficulty as far as possible. The journals were increased to the more usual pro¬ 
portions of 8 ins. X 4 f ins., but the wheel base had still to be kept down to 6 ft., and as the 
motors were larger than on the experimental trains, it was found necessary to dispense 
with a spring support for the motor. This, however, was considered the lesser evil of 
the two. The only other point in favour of outside-hung motors is that when only one 
motor is used on a bogie, suspending it outside the axles will greatly increase the 
weight on the driving wheels. Such an arrangement is undoubtedly preferable to the 
use of “ maximum traction ” bogies with unequal wheels, and will give all the adhesion 
required for any practical acceleration on the comparatively clean rails available in 
railway work. It is not, however, a desirable arrangement except for quite moderate 

452 


TRUCKS 


speeds. It is also only applicable to single cars, since, if there is more than one car 
on the train, it is undoubtedly correct practice to have a motor bogie and trailer bogie 
on each motor car rather than to have one motor on each bogie. In fact, even in the 
case of single cais, no gieat objection can be taken to having one motor bogie and one 
trailer bogie, since the experience of several English railways with steam motor 
coaches goes to show that they run quite satisfactorily whether the engine end 
is leading 01 ti ailing. I he advantages of placing both motors on one bogie are— 

(1) A cheaper type of bogie can be used for the trailer. 

(2) A hen motor bearings, gear, etc., have to be removed, only one bogie has to 
be removed. 

(3) Car wiring is greatly simplified and reduced in quantity. 

Ihe method of carrying the electrical contact devices on the bogie is really more 
a question of electrical equipment than of rolling stock design, since it obviously 
depends on the system of distribution more than on any other point. It has come to be 
a recognised principle in all the more modern installations that the contact shoe shall be 
suspended from a point at a fixed distance above the rail, in order to reduce the play 
between the shoe and the suspension. On the City and South London Railway, liow- 
evei, the shoes were originally suspended from the locomotive under-frame, and this 
anangement having been found to work fairly satisfactorily, is still continued on that 
railway. The authors, however, are of the opinion that the balance of advantage 
rests with the suspension at a fixed height. In order to secure this fixed height, the 
suspension must be attached to the axles, axle-boxes, or equalisers. The first of these 
is adopted on the Central London, where the third rail is in the middle of the four- 
foot way. The shoes on the motor bogies are suspended from a plank attached to the 
motor suspension bearings on the axle. A preferable arrangement on general grounds 
would undoubtedly have been to attach the plank to the equalisers, the shoe being 
under the transom. This arrangement was used on the bogies for the locomotives 
with geared motors. The wheel base of the motor car bogies, however, is so short 
that the shoes would have been almost inaccessible, and dangerously close to the 
motors. On the trailer bogies 1 of motor cars the plank may be attached to special 
bearings on the axle, and held from rotating by links attached to the end cross 
members of the bogie frame. This again is not recommended as an ideal arrangement, 
but was adopted as the best for the confined space available at the trailer end of the 
coach. 

The second arrangement—suspension from the axle-boxes—is adopted on the 
North-Eastern and the District Railways, and is, in fact, practically standard on non- 
equalised bogies where the third rail is outside the four-foot. The shoe plank is in 
these cases attached to lugs on the boxes. The third arrangement is used on the 
Lancashire and Yorkshire Railway, and is the usual one with equalised bogies where the 
third rail is outside the four-foot. If the wheel base is long enough to give proper 
clearance from the motors, it may also be employed with a third rail in the four-foot 
way, and, as stated above, it was so used on certain bogies on the Central London 
Railway. 

With regard to axle-boxes there is but little difference between practice in this 
country and America, the standard arrangement in either case being a cast iron or steel 
box having a circular opening at the back fitted with a “ dust-guard ” or “ oil-guard ” 

1 This applies to cases where it is required to provide shoes on both bogies of the motor car so 
as to bridge the gaps in the third rail at points and crossings. 

453 


ELECTRIC RAILWAY ENGINEERING 

of leather or similar material, and an opening in front to allow access to the 
journal and brass, with a removable cover. In this country the standard railway 
practice is to have this cover a machined fit on the front of the box, and secuie it 
with bolts passing through lugs on the cover and the box, and it is usual to specif}^ 
that the box should be watertight. The standard practice in America as laid down by 
the Master Car-builders’ Association, however, is a sheet iron cover opening upwards 
and outwards, and held closed by a flat spring. The Master Mechanics Association 
standard arrangement of this type of box, which has also been adopted by the American 
Street Railway Association, is for the cover to open edgeways, it being pivoted at one 
side and pressed against the box by a helical spring on the pivot bolt. M hen closed, 



Fig. 423. Master Car-Builders’ Standard Axle-Box for a 4|" x 8" Journal. 


the cover rests between two projections on the box, and to open it it is pulled out¬ 
wards to clear these projections, and is then pushed upwards or downwards. Both 
these arrangements have been used a great deal in this country. The machine-fitted 
front is, however, decidedly preferable, as the sheet iron cover seldom retains its 
shape well enough under service conditions to keep out dust or prevent undue spilling 
of oil, and is, moreover, easily torn off. 

The bottom of the box below the level of the openings forms an oil well, and in 
English practice there is usually a lip round the box, just below the level of the 
openings. The journal is lubricated either by means of oil-soaked waste with which 
the box is packed, or preferably by means of a cotton wick carried on a wire frame 
made to fit roughly the round exposed part of the journal, and pressed up by light 

454 

























































































































































Long. Section 


Front View 


Note:- The dia of this screw wit! be 
increased from */i' to ¥4 



Fig. 424. Kokbully Axle-Box. 














































































































































































































































































































































































































































































TRUCKS 


springs. This latter arrangement is the one generally adopted in this country, and 
gives very satisfactory results. The box is provided with machined facings for the 
brass or for the keep, which is placed between the box and the brass, as the case may 
be, at the top and the upper part of the sides. The axle-box originally employed on 
the trailer bogies of the Central London Railway, shown in Fig. 422, is typical 
of English practice, being a modification, to suit the smaller size of journals, from 
those of the Great Western Railway. American practice is illustrated by the 
standard Master Car-builders’ axle-box for a 4^-in. x 8-in. journal, shown in 
Fig. 428. 

Both types are found quite satisfactory for steam railway service where the 
passenger stock can be overhauled in detail at the end of each run, and the goods 
stock usually runs at a low speed, and has a very low yearly mileage. For electric 
railway conditions, however, where rolling stock is in service for 16 or 20 hours a 
day for long consecutive periods, and may run several thousand miles without coming 
in for repairs, it takes a considerable time to attend to at the end of the day's work, 
even if spring lubricating wicks are used, and with waste packing things will evidently 
be much worse. On the Central London Railway a box with an internal removable 
oil well has lately been adopted with good results, and is now the standard arrange¬ 
ment on that railway. The well consists of a sheet tin tray in which is placed the 
spring frame carrying the lubricating wick. The opening in the front of the box 
extends to the bottom, so that the tray can be slid in and out, carrying the 
lubricating wick with it. The axle-box for this arrangement is shown in Fig. 422. 
With this arrangement, however, there is more leakage of oil than is desirable, 
especially on a tube railway, and a certain number of bogies have been fitted 
experimentally with the Ivorbully axle-box, which is very largely used on the Con¬ 
tinent. This box is illustrated in Fig. 424. It is of an entirely different type 
from either the English or American standard patterns, and requires no packing or 
wicks. The whole axle-box practically forms one oil well, there being no opening 
at the front end, except a small hole at the top for renewing the supply of oil, 
and the back end being fitted with a leather packing, which is kept pressed against the 
journal by an adjustable steel band. The brass entirely surrounds the journal, and 
has an oil way at the bottom. This axle-box requires very little attention owing to 
the absence of packing, and will run without refilling for weeks at a time, effecting 
great economy in oil and improving the condition of the permanent way. 

The clearance between the sides of the axle-boxes and the axle guards should 
not exceed To i n - i n the longitudinal direction of the bogie, and should preferably be 
merely a slack fit. The same applies to the transverse travel if both outward and 
inward travel are limited on each box. In many cases only the outward travel is 
limited, each box being prevented from travelling inwards by the end thrust of 
the axle bringing the other box up against the opposite axle guard. 

The standard bearing for both coach and wagon journals both in this country 
and America is a single bronze casting resting on the journal. With regard to 
material, standard practice is a copper-tin alloy, with small proportions of zinc and 
lead, the lead being added as a reducing agent for purely manufacturing reasons. 
The following would be a very suitable alloy— 


Copper 
Tin . 
Zinc . 
Lead . 


80 to 88 per cent. 
18 to 10 „ ,, 

2 „ „ 

0-5 .. ,, 


455 


ELECTRIC RAILWAY ENGINEERING 


The standard American composition is— 

Copper 
Tin . 

Lead . 

Phosphorus 


80 per cent. 
10 „ „ 

9-5 „ „ 

0-5 


Phosphorus, of course, has a similar reducing effect to zinc, besides hardening 
the alloy. Special alloys, such as Stone’s bronze, are also largely employed, but the 
composition of these is naturally kept secret. Anti-friction metals of various composi¬ 
tions are also used a great deal. It does not appear, however, that there is any 
definite advantage in their use, unless, owing to special circumstances, the journals are 
of abnormal proportions ; for instance, it may be necessary to use very short journals 
owing to restricted space, in which case the journal will have to be abnormally large in 
diameter, thus raising the journal speed, or the pressure per square inch will be 
abnormally high. With ordinary proportions, however, and with pressures limited to 
the figures already given, white-metal should be quite unnecessary as far as cool 
running is concerned, and the earlier chapters of this book will have made it clear that 
the proportion of energy employed in overcoming journal friction is quite small, 
whether the service be one of frequent stops and high acceleration, or few stops 
and high speed. If it is employed, it should be on bronze and not on a cast-iron 
backing, as the best of white metals will run occasionally, and the results to the 
journals will be disastrous, if the bearing has only a cast-iron backing. The brass 
usually embraces about one-third of the diameter of the journal. In some cases, the 
brasses on driving axles are brought further down at the sides to take up the motor 
thrust. There is no particular necessity for this, however, since the side thrust due to 
the motor must obviously be much less than that due to the brake block, which exists in 
the case of trailer cars also. The case is, of course, quite different from that of a steam 
locomotive journal, where the side thrust may often exceed the load on the journal. 
In any case the lower ends of the journal should be well rounded with a large radius, 
so as to avoid scraping the oil off the journal. The brass is usually bored from 
3 Y in. to W l n * slack on the diameter. In the writers’ experience, the amount of 
slack should not exceed the smaller figure when both journal and brass are new. 

In order to limit the end play of the journal in the brass, the latter usually rests 
between a shoulder on the inner end and a collar on the outer end of the journal; a 
certain amount of play is allowed between the two, the standard practice in America 
being to allow \ in. This is an excessive amount for a driving axle, since, for reasons 
that have already been given, it is undesirable to allow much end play where a motor 
is supported on the axle. A new brass should preferably be merely a slack fit, and 
should certainly not have more than jY in. play on the journal; this, of course, 
involves careful fitting in order to ensure that the brass bears properly on its whole 
surface and not merely on the shoulder of the journal. In some cases, where, in order 
to save room, the axle-box has to come very close up to the wheel, and the diameter of 
the axle where it passes through the box has to be kept down, the intermediate 
shoulder between the journal shoulder and the boss for the wheel centre is omitted, 
the axle being reduced in one step from the diameter in the wheel boss to the journal 
diameter. In this case, the end play of the journal is taken up either by bringing the 
end of the brass down over the end of the axle or b}^ a separate end brass or keep, 
which is attached either to the brass or to the axle-box lid. This arrangement is usually 
only employed ( 1 ) on bogies which have to be got into an unusually small space, as in 

456 


TRUCKS 


the case of the Central London and the Manhattan Elevated Railways, or (2) on bogies 
which, as in the case of the Lancashire and Yorkshire (Fig. 402) and the American 
Ftieet Railways Association standard for 50-ton cars, Fig. 434, carry exceptionally heavy 
loads without being abnormally wide or requiring abnormally long or wide axle-boxes. 
When this arrangement is adopted, the whole of the end thrust is taken up on the 
end bearing of the axle. The brass is in this case fitted to the top and upper part 
of the sides of the axle-box, and its end play is limited either by a shoulder at 
its inner end or by a transverse feather engaging in a recess in the top of the box. 
The brass is sometimes provided with ribs, which are fitted to corresponding ribs in 
the box to avoid machining the whole surface. The standard arrangement of a journal 
with shoulders at each end will be found the better one on general grounds, and should 
not be abandoned unless there is some special reason, such as that given above. With 
shouldered journals, it is usual to have a packing piece termed a keep, or in America 
a wedge, between the brass and the axle-box. The object of the keep is to enable the 
brass to be removed with a smaller relative movement of axle and box than would 
otherwise be necessary for the brass to clear the collar. The collar being from 4 in. 
to | in. deep, the opening at the back of the box would be inconveniently large. The 
keep, however, is usually held from outward movement only by a small rib, so that 
by jacking up the box a short distance the keep can be removed and the brass lifted 
off the journal. In this country the top of the journal is usually a machined fit 
against the under-side of the keep, the sides of the journal and the top of the keep 
having machined ribs fitting against corresponding ribs on the sides and top of the 
axle-box. In America they are usually left rough, and either the back of the keep or the 
back of the journal is rounded so as to give a self-aligning bearing. The rounded keep 
is the more modern plan and the standard practice of the Master Car-builders’ Associa¬ 
tion. A certain amount of slack has to be allowed between the keep and brass and the 
axle-box. For motor bogies, the total play of the brass in the box should not 
exceed in. With a clearance of T U in. for the brass on the journal and T U in. for 
the box in the axle guards, there will be a total of T Vm* end play on the axle. This 
should be looked on as an outside figure for a bogie leaving the shop; and, as already 
stated, the writers much prefer merely slack fits throughout. The total end play of 
the axle should be sufficient, however, to ensure that there is no binding in either 
longitudinal or transverse direction. 

Table CXXI. gives the journal pressures in use with various axles in pounds per 
square inch of the projected area of the journal. It will be noticed that from 200 to 
250 lbs. per square inch is about the usual pressure, and in this country similar 
pressures are also employed in locomotive work. American locomotive practice, how¬ 
ever, is much more conservative. Meyer (“ Modern Locomotive Construction ”) gives 
it as his opinion that the pressure should be kept considerably below 160 lbs. per 
square inch, if the journal speed exceeds 9 ft. per second, which, with ordinary pro¬ 
portions of wheels and axles, would correspond to a train speed of about 60 miles per 
hour. Probably the difference is due to the much greater care taken in fitting 
journals and brasses in this country. For high speed electric service, owing to the 
comparatively small wheels, journal speeds will generally be exceptionally high, and 
in such cases 200 lbs. should be considered the limit, but for urban services at, say, 
15 or 20 miles an hour average speed, 250 lbs. is quite safe with proper workmanship 
and reasonable supervision. 

With regard to axles, long experience has determined certain dimensions and 
maximum working stresses as desirable in the interests of safety and economy, and it 

457 


ELECTRIC RAILWAY ENGINEERING 


can seldom be advisable to depart from these. Indeed, the tendency is all in the 
direction of increasing axle diameters for a given load, since it is found that, owing to 
the dead weight of the motors, the axles are subjected to almost as severe shocks as 
those of steam locomotives. Table CXXI. gives some comparative figures of the standard 


Table CXXI. 
Journal Pressures. 










- 

O a> 

! g v. . 

3 S3 O g 

=E £uA 


Axle. 


Fig. 

0 'H 

G O 

Dimensions in Inches 
(Fig. 435). 

1 0 73 0 

a, k c; <5 
TJ ^ 

•— 1 G z 
zz a) 40 

£t? 

£ 8 ~ ~ 

A 

f-. 

a 




O Ph 





O Cm 

2 ° B - 

0 £ 

03 




O 

A. 

B. 

C 

D. 

? O 

c •- <»£ 

S ^ ^ GG 

03 


English standard | 

10 -ton wagon 

425 

8,400 

8 

3-75 

9-80 

5-25 

30 

280 

5,700 


for private-! 
owners’ wagons ( 

15-ton ,, 

426 

12,000 

9 

4-50 

10-00 

5-75 

40-5 

296 

6,400 


20 -ton ,, 

427 

16,000 

10 

5-00 

10-00 

6-75 

50 

320 

5,300 

<D 

American M.C.B. f 

40,000-lb. car 

428 

7,700 

7 

3-75 

8-50 

4-875 

26-2 

294 

5,700 

P 

pit 

standard . . \ 

60,000-lb. „ 

429 

10,500 

8 

4-25 

8-50 

5-375 

34 

310 

5,800 

'B 


15-ton elec- 










CT 1 

a> 


trie car 

430 

3,400 

6 

3-25 

8-125 

3-75 

19-5 

175 

5,200 



20 to 28-ton 










c3 

American Street 1 
Railways Asso-< 
ciation standard 1 

1 

electric car 

431 

6,560 

7 

4-00 

9-50 

5"125 

28 

234 

4,700 

T_ C$ 

30-ton elec¬ 
tric car 
40-ton elec- 

432 

7,000 

8 

4-25 

9-625 

5-375 

34 

206 

4,500 

eg 

O 

fcO 


trie car 

433 

9,400 

9 

5-00 

10-125 

6 - 375 

45 

210 

3,700 

' (J 

P 


50-ton elec- 












trie car 

434 

12,000 

9-25 

5-50 

8-50 

6-50 

51 

235 

3,700 


Central London 1 











r~| 

Railway motor r 
axle . . . i 



7,800 

8 

4-625 

8-00 

5-75 

37 

210 

3,300 

S 











is 

Manhattan Elec-1 











$-1 

trie Railway! 
motor axle . 1 



6,800 

8 

4-25 

8-50 

5-50 

34 

200 

3,500 

0 


axles adopted by the English railway companies for private owners’ wagons, by the 
Master Car-builders’ Association of America for freight cars, and by the American 
Street Railways Association for electric cars. The Table also contains a few examples 
of axles actually in use on electric cars. These axles are also shown in Figs. 425 to 
435. In order to obtain a uniform basis for comparison in computing the bending 
stresses, the load is assumed distributed along the whole of the brass, the wheel 
flanges assumed to be equidistant from the inside of the rails, and the distance 
between points of contact of wheels and rails assumed to be 4 ft. 10 ins., owing to the 
coning of the wheels and the radius of the rail table (see Fig. 435). Comparing the 
conditions under which motor-driven and trailer axles have to operate, it may be 
pointed out that whereas the bending moment of a trailer axle is a maximum at the 
points vertically over the points of contact of wheels and rails, 1 and is uniform between 
those points, the bending moment in a motor-driven axle is usually slightly greater at 
a point between the wheel centres, namely in one of the motor supporting bearings 

Neglecting the weight of the axle itself. 

458 


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TRUCKS 


(with a geared motor), or iii the spider of the armature if carried on the axle. The 
stresses to which the trailer axle is subjected are bending moment and shear due to— 

(1) The load; 

(2) The pressure of the brake block when brakes are set (with single blocks); 

(3) The backward thrust of the axle when brakes are set. They are subjected to 
torsion due to—- 

(4) Unequal travel of the wheels on curves. 

Of these stresses (2) is fixed by the wheel load as described in dealing with 
brakes, and (3) and (4) are obviously limited by the wheel load and the coefficient of 
adhesion of wheel and rail. With regard to (1), since certain parts—equalisers, axle- 
boxes and fittings, and the axle itself—are not carried on springs, they will from time 
to time apply forces equal to several times their weight, the greater part—the weight 
of the axle—being between the wheel hubs. 

The additional stresses to which a motor-driven axle is subjected are— 

(5) Bending moment and shear due to the forward thrust of the motor drive; 

(6) Torsion due to the motor drive. 

Both these again are limited by the wheel load and the coefficient of adhesion to 
the same values as (2) and (3), so that for a given load the driving axle will, as far as 
they are concerned, have no more to stand than a trailing axle. Here again the 
conditions of a motor-driven axle are quite different from those of a steam locomotive 
driving axle. In nearly all cases, however, the stresses due to (1) are much higher in 
the driving axle than in the trailing axle, since the unspring-borne load will, in the 
majority of cases, be a much larger proportion of the whole. If the motor is gearless, 
the armature almost always, and the field magnets in many cases, are not spring- 
supported, while with geared motors there are usually bearings on the axle to keep 
the gears properly meshed. In either case a force equal to several times the weight 
of the motor will be momentarily applied from time to time. 

It is important to bear in mind that the maximum bending stresses will be much 
larger than those given in the table. For instance, in passing round a curve the flange 
of the wheel pressing outwards will increase the distance C, and the load on the outer 
journal, besides causing additional bending due to the thrust on the wheel. Worn 
wheels and rails will also increase the distance C, a badly fitted brass may concentrate 
the load towards the outer end of the journal, whilst comparatively small irregularities 
in the road may easily double the load on the journal. The side thrust due to the 
brake block has already been dealt with. 

It therefore becomes necessary to design motor driving axles considerably 
more liberally than trailing axles for the same load. A further reason which 
necessitates liberal design is- the existence of keyways for securing the armature 
or gear wheel, as the case may be, to the axle. The actual reduction of strength 
for a static load caused by this is inconsiderable, but, as is well known, cracks 
are always liable to start from the corners of holes and keyways in shafts or 
axles. This consideration is of such importance that the Committee on Standards 
of the American Street Railways Association, in their report in 1902—which was 
adopted by the Association—recommended that the axles should be so much enlarged 
at the gear 'wheel fit that the distance from the axis of the axle to the bottom of the 
keyway should be the same as the radius of the axle in the driving wheel hub. This 
appears to the authors to be somewhat unnecessarily large, and results in an objection¬ 
able shoulder immediately inside the wheel hub, but there is no doubt that the 
recommendation, since it errs on the side of strength, errs in the right direction. 

459 


ELECTRIC RAILWAY ENGINEERING 


The disadvantages of having keyways to the axle have led to the introduction of 
several devices to render them unnecessary. The best known is probably that of 
Messrs. Doyle and Brinckerhoff, which was adopted on the Metropolitan West Side and 

the Manhattan Elevated Railways, where a solid gear wheel is 
shrunk on to an extension of the driving wheel hub, as shown in 
Fig. 436. This method, of course, has the obvious drawback that, 
in order to remove the gear wheel, the driving wheel has to be 
removed from the axle. This might be got over by using a split 
gear keyed on to the extended hub, but, with the large hub 
necessitated by this arrangement, it would be difficult, if not 
impossible, to find room for the bolts for holding together the 
split gear wheel. 

With regard to material, the sizes of axles adopted by the 
Master Car-builders’ Association are intended for either wrought 
iron or mild steel. Mild steel is practically universal for electric 
traction purposes, the most suitable material having an elastic 
limit of about 20 tons and an ultimate tensile strength of 33 
to 38 tons per square inch, with not less than 40 per cent, 
reduction of area at fracture and 25 per cent, elongation in a 
2-in. length. The rough axle should stand, without breaking, 
sixteen blows from a 1-ton tup, falling 25 ft. on the centre of the axle, the latter 
resting on supports 3 ft. 9 ins. or 4 ft. apart, the axle to be turned after each blow. 
Two per cent, of each batch of axles should be thus tested. 

Cast steel has been employed with some success for locomotive crank axles, but 
there appears to be nothing to be gained by its use for straight axles. Table CXX1I. gives 
a list of various qualities of steel for axles. Nos. 1, 2, and 6, are specification figures, 
and the remainder are test figures. Nos. 2 and 3 are respectively the specification 
and test figures for the nickel steel in use in certain of the Central London motor 
axles. 



Fig.436. Manhattan 
Wheel. 


Table CXXII. 

Various Qualities of Steel for Axles. 


Number. 

Maker and Descriptio i. 

Elastic Limit, 
Tons per Square 
inch. 

Breaking Strain, 
Tons per 
Square Inch. 

Elongation, 
per cent. 

Reduction 
of Area, 
per cent. 

1 

Manhattan Elevated Railway, motor 
axle ...... 

Not less than 
17-9 

357 


— 

2 

Krupp, Siemens-Martin 

— 

28 

30 


3 

Krupp, 80-ft. nickel steel . 

24 

32 

30 

_ 

4 


2413 

333 

41 

65 

5 

J. Baker & Co. ... 

— 

36 

27 

53 

6 

S. Fox & Co. ..... 

— 

36 

29 

51 


1 or attaching wheels, whether driving wheels or otherwise, to axles, the authors 
have always found a press fit without keys to be quite satisfactory. As the axles do 
not have to transmit such severe torsional shocks as those of steam locomotives, keys 
aie usually unnecessary, and it is an obvious advantage to avoid the use of keyways in 

460 








































TRUCKS 


the driving axle where possible. On the Central London Railway the wheels, which 
are 84 ins. in diameter, are pressed on to the axles, which are 5f ins. in diameter in the 
wheel fit, with a pressure of not less than 50 tons or more than 60 tons. The tractive 
force exerted by the motor at full rated load is about 3,200 lbs. at 17-in. radius, 
and the sharpest curve on which these trains run is 150-ft. radius. A good general 
role when keys are not employed is to allow 10 tons pressure for every inch of axle 
diameter in the wheel seat. 

With regard to wheel centres, there appears to be little to choose between wrought 
iron and soft cast steel. The former material is perhaps more generally employed, but 
a cast steel of about 28 to 32 tons per square inch ultimate tensile strength and 
a minimum elongation of 15 per cent, in a 2-in. length is found to give good results 
in locomotive practice, and should therefore be quite satisfactory for electric traction, 
especially as the castings are somewhat simpler in form. It must be borne in mind in 
dealing with wheel centres generally that the wheels of electrically driven vehicles, 
like the axles, are subject to heavy shocks due to the fact that a considerable propor¬ 
tion at least of the weight of the motor is carried direct on the axle. Where gearless 
motors are employed, with the entire weight of the motor carried without springs, 
considerable trouble has been experienced from time to time by failures of wheel 
centres, even where these were of exceptional strength judged merely by the load. 
For wheels other than driving wheels a wood centre is, of course, quite suitable, and 
possesses several advantages which need not he discussed here, as they are well known 
in ordinary railway practice. In tube railways they are particularly advantageous on 
the score of noise. Tyres are usually secured to the centres by a lip on the side of the 
wheel centre and by a locking ring, which should be shrunk on at a low heat. 
Fig. 437 shows the standard sections of tyres and fastening rings approved by 
English railway companies for private owners’ wagons. In the case of driving 
w'heels it is a common practice to omit the locking ring and secure the tyre by means 
of the lip and by studs screwed through the rim into the tyre from the inside. An 
example of this will be noticed in the Lancashire and Yorkshire bogie (Fig. 402). 
Another method, illustrated by No. 4 of Fig. 437, and also by the Manhattan driving 
wheel (Fig. 436), is to have two locking rings and secure these and the tyre to the 
centre by means of bolts parallel to the axle. The standard width and depth of rail¬ 
way tyres having been arrived at as the result of long experience, they should be 
adhered to unless there is some substantial reason for departing from them. The 
standard width of tyre in this country for coaches and wagons is 5 ins. For driving 
wheels it is desirable to follow steam locomotive practice and make the width 54 ins. or 
at least 5J ins., especially if, as will happen in many cases, the train is to be pushed 
from the rear, as well as pulled from the front. Narrow wheels are very objectionable, 
as they travel badly, cause undue wear at points and crossings, and, indeed, necessitate 
extreme care to avoid frequent derailments at these places. For tube railways, how¬ 
ever, where, as has been pointed out above, the allowable wear on wheel treads is 
small, it is permissible to employ a thin tyre, as otherwise tyres will have to be 
replaced before they are rendered unserviceable by their thinness. In order to obtain 
the best material to ensure safe and economical running, it is necessary to consider 
carefully the type of service in which tyres are to be employed. For railways with 
numerous stops, which implies heavy wear due to braking, a hard tyre is desirable ; 
and as speeds under this condition will be comparatively low, such tyres can be 
employed with safety, whereas, at very high speeds, an extremely hard tyre may 
be undesirable and will not be so necessary owing to the conditions of service. For 

461 


ELECTRIC RAILWAY ENGINEERING 


tube railways, it is of particular importance that the hardest tyre consistent with 
safety be employed, since the allowable variation from the standard loading gauge is 
usually small, and the depth of wear on the tyres is consequently less than in ordinary 
practice. Several qualities of steel, recommended by various makers, are given in 



No. 1. 




I—'«H 



No. 4 . 


Tyre Sections (Issued 1904). 


Table CXXIII. Nos. 1 to B are specification figures ; the remainder are from actual 
tests, Nos. B and 4 being respectively the specification figures and the test figures for 
the same steel. It has been found that for tube railway work a steel of No. 6 quality 
is far too soft, and even No. 5 necessitates frequent turning up of the wheels. On the 

462 












































































































TRUCKS 


Central London Railway there are a number of wheels with tyres of No. 3 steel; they 

lave not been m service long enough to form a definite opinion of the material, but so 

ai they have proved quite satisfactory, and the wear appears to be much less than on 

he other tyres. Two per cent, of each batch of tyres should be subjected to the 
falling weight tests. J 




Maker and 
Description. 


■n \ 
tc l 


>~i x 

« c 
o 
H 


1 Brown, Bayley. j 48 


2 Krupp, Siemens- 50 

Martin 

3 Krupp, crucible 30 

steel 

4 Krupp, “ C.H.” 70 

steel 

o Krupp, “C.H.” 
steel 


6 J. Baker & Co. . ! 50 


7 Original trailer 38 
car tyres on 
Central Lon- 
j don Railway 


Table CXXIII. 
Qualities of Steel for Tyres. 



c3 

O 

Elongation, 
per cent. 

•3 . 

«*-. if 

0 S 

C O 

.2 ^ 

43 a? 


a; 



14 


12 

12 


12 

15 

32 

21-5 

39 

I 

23 

40 ; 


Tyre to stand deflection of ^ of original diameter. 
Analysis : Carbon, 0'6 per cent.; silicon, 0"25 per cent.; 
sulphur, under 0 - 04 per cent. ; phosphorus, 0 - 04 
per cent.; manganese, 0'70 per cent. 

One-ton tup falling from 5, 6, 7, up to 10 ft. till internal 
deflection, 10 per cent, of diameter. 

Two blows each at 10 and 15 ft. from 1-ton tup. 

Two blows each at 10, 15, and 20 ft. from 1-ton tup. 


Diameter of tyre, 28f ins. (internal). 

Blow from 1-ton tup 10 ft. internal diameter 

10 
15 
15 
20 
20 
25 
30 

Blow from 1-ton tup, first blow 8 ft., deflection 


10 

12 

14 

16 

18 

20 

30 


: 28* 

: 281 
: 27g 
: 27f 
27-’- 
26* 
26* 
25“ 
i in. 

t „ 

1 * ins. 

If „ 

n „ 

3* „ 

3f| „ 

,, 


ins. 


3* ins. 


= 90 tons. 
= 95 


463 


























Index 


Acceleration, 21 et seq. 

Distribution of tractive effort amongst axles, 29 

Electrical Equipment Weight, 43 

Energy required for, 18 

“Motor Curve,” 25, 32, 48, 62, 60 

Power, 

Amount required during, 31 
Patio of maximum to average power at axles, 
51 

Relation of maximum to average input to train 
80 


Schedule Speed Limitations, Method of Investi¬ 
gating, 34 

Series Motor Characteristic, 32 
Steam versus Electric Service, 29. 34. 51 
Variable rate of, effect on Polling Stock and 
Permanent Way, 32 
Accumulators, 

Comparative Cost of Plant with and without, 
200 


Use of in Sub-stations, 191 
Adhesive Coefficients, 326 
Air, 

Compressor, Motor-driven, 336 
Pumps, 112 
Edwards’ type, 118 

Pesistance, Eelation to Total Resistance, 10 
Algemeine Elektricitats Gesellschaft, 

High Speed Motor Car used for Berlin-Zossen 
Tests, 362 

Winter-Eichberg type of Motors, 394 
Allen, A. H., on Central London Railway Sub- 
Stations, 212 
Alternating Current, 

Current Values in Track Pails, 286 
Equijiments, see Electrical Equipments 
Generators, see Generators 
Motors, see Motors 
Resistance of Pails to, 280 
American Bogie Truck, 433 

Brake Foundation iu Trailer Bogie, 446 
American Locomotive Co., Electric Locomotives 
for New York Central Railway, 292 
American Master Car-builders’ Association, 
Axle-Box, 454 
Axles for Freight Cars, 458 
Material, 460 

Brake Heads and Shoes, 449 
Rounded Keep for Journal, 457 
Swing Bolster, 434 

American Society of Civil Engineers, Recommen¬ 
dations for Track Rails, 269 
American Street Railway Association, 

Axle Box, 454 
Axles for Electric Cars, 458 
Standards Committee Recommendations, 459 
Motor Bogies, Play of Journal in Brass, 457 
Anderson, E. II., on Speed-time Curves, 53 


Armature, 

Effect on design of Fly-wheel, 104 
Magnetomotive Force, 176 
Method of Mounting on City and South London 
Locomotive, 315 
Rotational Energy of, 21, 448 
T. v Pe to be employed with Compound-wound 
Synchronous Motors, 175 
Armstrong, on 

Effect of frequent stops in high-speed rail¬ 
roading, 84 

High Schedule Speeds, 91 
Light versus Heavy Trains, Tractive Force re¬ 
quired, 87 

Live Load Percentage, Note 13 
Some phases of the Rapid Transit Problem, 23 
Ashe, S. W.—Starting Converters, 205 
Ashe and Keiley on Ratio between dead and told 
Weight of Cars, 13 
Aspinall, on 
Air Resistance, 10 

Comparison between heavily loaded and lio-ht 
trains, Note 11 
Tractive Resistance, 4 et seq. 

Auxiliary Apparatus for New York Central Loco¬ 
motive, 296 
Avery Weigher, 124 
Axle(s), 

Attachment of Wheels to, 460 
Boxes, 453 

Distribution of tractive effort amongst, 29 
Guards for Bogies, 435 

Maximum instantaneous Power required, 44, 49 
Power and Energy, Eelation of to Tractive 
Force, 40 

Ratio of Maximum to Average Power, 51 
Recommendations of American Street Railway 
Association Standards Committee, 459 
Standard for Freight and Electric Cars, 458 
Steel, Various qualities for, 460 
Weight of Motor on, 451 


Babcock and Wilcox Water-Tube Boilers, 129 

“Baggage Car” type of Paris-Orleans Electric 
Locomotive, 324 

Baker Street and Waterloo Railway, 

Conductor Rails, Method of Mounting and 
Insulating, 251 
Insulators, 250 

Baltimore and Ohio 1S96 Gearless Locomotives, 
Data, 307 
Trucks, 431 

Baltimore and Ohio 1903 Geared Locomotives, 
310, 386 
Trucks, 431 

Barbier on Power absorbed by Locomotive com¬ 
pared with Train, Note 12 


E.R.E. 


465 


H H 


INDEX 


Barometric Condenser, 110 

Barrett, Brown and Hadfield—Test Results, 247, 
248 

Basic Open-hearth Rails, 269 
Battery-Booster Set, 192 

Bearings—Standard Composition for Coach and 
Wagon Journals, 455 

Berlin-Zossen Tests, 5 et seq., 172, 362, 391 
Camp’s Concise Resume of, Note 6 
Bessemer Steel Rails, 269 
Blood’s Formula, 87 
Board of Trade Regulations on. 

Earthed Conductors, 277, 284 
Supporting Suspension Cables, 259 
Voltage drop in uninsulated Conductors, 241 
Bogie Trucks, see Trucks 
Boilers, 107 

Mechanical Stokers versus Hand Firing, 109 
Bolsters, Swing and Rigid, 434 
Bolts, Inferiority of to Rivets, 440, 443 
Boosters, 

Compound-Wound in series with Battery, 192 
Track, Arrangementfor Alternating Current, 284 
Brake(s), 

Foundation Work, 445, et seq. 

Heads, 449 
Shoes, 

Energy dissipated at during Retardation, 23, 
48 

English and American types, 448 
Braking, 

Gradients, 81 

Rate of Retardation during, 23 
Regenerative Control methods of Restoring 
Energy, 46 
Brill Truck, 435, 441 
Bristol Tramways, 

Generating Plant, 115 
Plan of Power Station, 124 
Type and Capacity of Plant Installed, 126 
British Insulated and Helsby Cables, Ltd.— 
Cables furnished to London Underground 
Electric Railways, 158, 161 
British Thomson-Houston Co., 

Compensated Series Single-phase Motor, 396 
Overhead Conductor and Supports, 263 
Winter-Eichberg type of Motors, 395 
British Westinghouse Co., see Westinghouse Co. 

Cables, 

Concentric—Standard Thickness of Insulation 
and Lead Sheathing, 162 
Three-Core, 

Construction, 

Central London Railway, 156 
District Railway, 158 
Metropolitan Railway, 161 
New York Subway, 154 
Engineering Standards Committees’ Recom¬ 
mendations, 147 

Henlev’s Patent “Laminin” Conductor 
Cable, 162 

High Tension Cable Joint, 160 
High Tension Transmission System, Cost 
and Construction, 140 
Installation, 142, 153 

Maximum Current Densities permissible in 
Copper Conductors, 148 


Cables, contd. 

Three-Core, contd. 

Paper versus Rubber Covered, 150 
Standard Thickness of Insulation and Lead 
Sheathing, 162 

Temperature Distribution in, 149 
Ferguson’s Tests, 150 
Temperature Rise in, 148 
Twin—Standard Thickness of Insulation and 
Lead Sheathing, 162 
[See also Suspension Cables] 

Callender’s Cable and Construction Co.—Cables 
supplied for District Railway, 160 
Camp’s W. M. Resume of Berlin-Zossen Tests, 
Note 6 

Car Axles, 457 

Car Wheels—Ratio of Maximum to Average 
Energy at, 69 
Carbon, 

Effect on Conductivity of Steel, 247, 248 
Percentage of in Track Rails, 269 
Carriage Axle Boxes, 453 
Carter on, 

Adhesion Coefficient, 326 
Arrangement of Track Boosters, 2S4 
Energy Consumption, 80 

Kinetic Energyof Train due to Rotating parts, 21 
Location of Sub-Stations, 241 
Rated Capacity of Electrical Equipment, 84 
Rating of Railway Motors, 55 
Speed-time Curves, 53 

Tractive Resistance and Power required, 15 
Weights of Continuous Current Equipments, 88 
Weights of Single-phase and Continuous 
Current Motors, 389 
Cascade Control, 391 

Cascade Motor set of Valtellina Locomotive, 335, 
337 

Central London Railway, 

Axles, 458 

Method of Attaching Wheels to, 461 
Bogie Truck, 438 

Arrangement of Contact Devices, 453 
Parshall’s Design, 439 

Brake Arrangement, 441, 447, 450 
Play of Journal in Brass, 457 
Position, 452 
Brake Block, 449 
Cable Construction, 156 
Carriage Axle Box. 455 

Conductor Rails, Method of Mounting and 
Insulating, 251 
Crown Rail Bonds, 277 

Equipment Weight and Energy Consumption, 95 
Gearless Locomotives, Data, 317, 386 
G.E. 66A Motor, Employment of, 54 
Generating Plant, 101 
Cost and Comparison, 133 
Plan of Power Station, 115 
Type and Capacity of Plant Installed, 119 
Gradients, Energy supplied by, 18 
Insulators, 250 

Kinetic Energy of Armature, 448 
Latest Type of train, Motor Equipment, Data, 
etc., 57 

Operation of, 61 

Speed, Tractive Force and Power Calcula¬ 
tions, 68 


466 


INDEX 


Central London Hail way, contd. 

Starting Resistance, 4 
Sub-Station, Technical Data, 208 
Comparative Costs of Rotaries and Motor 
(venerators, 186 
Plan and Equipment, 212 
Tests, 


Rail Resistance to Alternating Currents 281 
tractive Resistance, S, 66 
Tyres, 463 

Centrifugal versus Reciprocating Pumps 111 
Chambers’ Patent Third-Rail Insulator, 251 
Channel Rail, Use of, 251 
Characteristics of Electric Railway Motors 54 
Chicago Rail Bond, 276 

Chimney—Height, Effect of on Draught, 10S, 115 
City and South London Railway, 

Conductor Rails, Method of Mounting and 
Insulating, 251 

Curves, Tests showing effect of on Tractive 
Resistance, Note 11 
Gearless Motors, 315 
Starting Resistance Experiments, 4 
Tractive Resistance Tests, 8 
Trucks, 431 


Arrangement of Contact Devices on, 453 
Clark, D. E. Formulae for Designing Semi- 
, Elliptical Springs for Locomotives" 444~ 
Clearing House Conference—Position of Con¬ 
ductor Rails, 255 
Coasting, 23 

Influence on Speed-time Curves, 76 
Reduction of Energy at Axles. 48 
Retardation due to Train Friction, 66 
Coefficients, 

Adhesive, Steam and Electric Locomotives, 
326 


Weight Coefficient of Railway Motors, 373 
Columbia Rail Bond, 277 
Commutation in Single Phase Motors, 415, 421 
Commutator, Deterioration of—.Single ' Phase 
versus Continuous Current Motors, 96 
Compensator, 

Connection of Three-phase Rotary with. 204 
Oil-Cooled Type, 402 

Compounding, Effect of a change in adjustment, 
183 


Condensing Plant, Type and arrangement, 109 
Conductors, 

British Standard Sizes, 147 
Construction and Supports, 162 
Maximum permissible current densities, 148 
Overhead System, 245 
Suspension Cables, 260 

Voltage drop in uninsulated—Board of Trade 
Restrictions, 241 
[See also Rails, Conductor.] 

Conduit Construction—Single versus Multiple 
Ducts, 153 
Contact Devices, 

Arrangement on Bogie Trucks, 453 
Hew York Central Locomotive, 297 
Paris Orleans Locomotive, 323 
Continuous Current, 

Generators, see Generators 
Motors, see Motors 
Overhead System, 245 
Track Rails, 286 


Continuous Current versus Single Phase System 
95, 360, 386, 419 * 

Carter on, 242 

Comparative Capital and Operating Costs, 425 
Deterioration of Commutator, 97 
Contour of Train, Effect of on Resistance, 10, 13 
Control System, 63, 69 

Baltimore and Ohio 1903 Geared Locomotive 
311 

British Thomson-Houston Single Phase Rail¬ 
way System, 403 

British Weslinghouse Single Phase Motors, 405 
Electro - pneumatically controlled Unit 
Switches, 411 
Cascade System, 335, 391 
Gradients versus, 81 

Xew York Central Electric Locomotive, 295 
Parallel versus Series Parallel, 74, 75 
Paris-Orleans Locomotive, 325 
Pneumatic Control Connections for Rheostat, 
335 

Regenerative Control Methods of Restoring 
Energy, 46 

Regenerative versus Series Parallel, 47 
Rheostat Loss, 58 
ValteUina Motor Cars, 343 
Ward-Leonard System, 351 
Converters, see Rotary Converters 
Cook, E. E., Trucks for District Railway, 439 
Cooling, 

Curve, 82 
Towers, 114 

Type of Condenser, 110 
Copper, 

Cost, 142 
Losses, 82 
Costs, 

Capital and Operating for Continuous Current 
versus Single Phase Railway Systems, 425 
Geared versus Gearless Equipments, 372 
Crane used on Central London Railway, 212 
Crown Rail Bond, 277 

Cserhati—Regenerative features at ValteUina, 338 
Current Density in Track Rails, 286 
Curtis Turbine Generator for operating New York 
Central Locomotive for tests, 298 
Curves, 

Comparison between Carter’s and Armstrong’s, 
85 

Effect of on tractive resistance, 11, 13 


Dawson on Weights of Single Phase and Con¬ 
tinuous Current Equipments, 388 
Dielectric, 

O’Gorman’s principle of Grading, 143 
Standard thickness, 164 

Strength of Cable insulated with Varnished 
Cambric, 141 
Distributing System, 244 
Protection of Live Rails, 251 
[See also Third Rail and Overhead Systems.] 
District, Metropolitan, Railway, see London 
Underground Electric Railways 
Diversity Factor, 69 

Draught — Chimney, Draught produced by, 
dependent upon height and temperature of 
gases, 108, 115 
Drifting, see Coasting 


INDEX 


Driving Wheel Diameter, 372 
Doulton’s Insulators, 250 

Doyle and Brinckerhoff’s Keyless Driving Wheel, 
460, 461 

Dublin United Tramways, 

Generating Plant, 115 
Cost and Comparison, 133 
Plan of Power Station, 127 
Type and Capacity of Plant installed, 130 
Ducts, 153 

Dudley, Dr. P. H., on 

Influence of rail on tractive resistance, Note 5 
Power absorbed by locomotive compared with 
train, Note 12 
Dynamos, see Generators 


Earle, Mr.—Cost of Cables, 187 
Earthed Conductors, Board of Trade Begulations, 
277, 284 _ 

Eastern Railway of France, Note 12. 

Ecole d’Electricite, Tests of Rail Bond Resistances, 
279 

Edwards’ Air Pump, 118 
Efficiencies, 

Continuous Current and Single Phase Motors, 
415 et seq. 

English and Foreign Power Stations, 134 
Thermal Efficiency of Power Station Plants, 136 
Eichberji', Development of Single-phase Commu¬ 
tator Motors, 393, 394 
Electric 

Cars—Motor Axles, 458 
Locomotives, see Locomotives 
Motors, see Motors 

Railway Service—Axle-box, type of, 455 
Traction versus Steam Traction, 13, 29, 34, 51, 
88 , 325 

New York Central Railway Tests, 301 
Valtellina Railway, 344 
Electrical Equipment, 

Carter’s Curve of Rated capacity of, 84 
Contact Devices, 297, 453 
Gear less versus Geared, Relative weights and 
costs, 372 

Locomotives and Motor Carriages, 291 
Overhead System, 245 

Single-phase versus Continuous Current Sys¬ 
tems, 97, 388, 422 
Weight, 29, 31, 43 

Baltimore and Ohio 1903 Geared Locomo¬ 
tive, 314, 386 

Central London Gearless Locomotive, 319, 
386 

Central London Railway, Percentage to total 
train weight, 95 

New York Central Locomotive, 293, 386 
Paris-Orleans Geared Electric Locomotive, 
323, 386 

Siemens and Halske high speed 10,000 volt 
three-phase Locomotive, 357 
Weight including Continuous Current Motors 
and Accessories, Carter’s data, 88, 94 
[See also Locomotives and Motors.] 

Electrical Power Genei’ating Plant, 101 et seq. 

[See also Generating Plant.] 

Elliott Bros., Leakage Indicators, 222 
Elliptical and Semi-elliptical Springs, 444 


Energy, _ ‘ 

Amount dissipated at Brake Shoes during 
retardation, 23 
Consumption, 

Axles, 40 

Central London Railway, 95 
Influence of Gradients, 80 
Employed in overcoming journal friction, 456 
Ratio of maximum to average energy at car 
wheels, 69 
Recoverable, 

Gradients, 81 
Percentage of, 47 
Regenerative Braking, 46 
Reducing, Methods of, 23, 4S 
Rotational Energy of Armature, 21, 448 
Supplying, Methods of, 18 
Engineering Conference—Position of Conductor 
Rails, 255 

Engineering Standards Committee, 

Insulation and lead sheathing for three-core 
and Concentric Cables, 162 
Stranded Conductors, 147 
Track Rails, 270 
Equalising Lever, 432 

Evaporation, Ileat transferred from water to air 
by, 114 


Fares, Difficulty of adjusting, 90 
Farnkam Co. of Chicago, Type of “ under con¬ 
tact ” third rail, 254 
Ferguson, L. A., on 

Conduit Construction, 153 
Temperature distribution in Cables, 150 
Field Excitation, 

Effect of re-arrangement, 183 
Series Motors, 54 
Field Magnetomotive Force, 176 
Finzi, Compensated Series Single-phase Commu¬ 
tator Motor, 395, 422 
Fly Wheel, 103 

Forest City Electrical Co., “Protected” rail 
bonds, 275 

Frame Design, Weaknesses, 442 
Freight Service, 

Freight weight, percentage of total train weight, 
12 

Standard Motor Axles, 458 
Friction, 

Journal, Energy employed in overcoming, 456 
Losses, see Losses. 

Train, 66 

Fuel, Thermal value, 108 
Furnace temperature, 107 


Ganz & Co., 

Italian State Railways, Polyphase Locomotive 
1906 type, 341 

Valtellina three-phase gearless locomotive, 326 
Gear Ratio, Effect on speed and tractive effort, 82 
Geared versus Gearless locomotives, 315, 325 
[See also Locomotives.] 

Gearing Losses, 55 
Geipel Steam Traps, 126 
General Electric Co. of America, 

Method of protecting live rail, 253 


468 


INDEX 


General Electric Co. of America, contd. 

Motors, 

Compensated series single-phase commutator 
motors, 395 

G. E. 66A motor, 54 et seq. 

G. E. 605 75 h.p. motor, 396 
New York Central Railway Electric Locomo¬ 
tive, 292 
Tests, 29S 
Rail Bonds, 274 

Resistance and Composition of Steel, Test 
results, 247 
Generating Plant, 

Arrangement, design and characteristics, 101 
et seq. 

Capacity, 243 

Condensing Plant, arrangement and type, 109 
Cost of operating and maintaining, 132 
Generator, Conditions to be fulfilled by Con¬ 
tinuous Current and Alternating Current 
type, 104 

Mechanical Stokers versus hand firing, 109 
Turbines versus high speed reciprocating 
engines, 101. 103, 113 

Generating System, see Generating Plant and 
Power Stations 
Generators, 

Alternating and Continuous Current type, 104 
Specification for, 

550 k.w. vertical cross compound Continuous 
Current Steam Generator, 104 
2,500 k.w. vertical three cylinder compound 
three-phase steam generator, 105 
Synchronous versus Induction motors, 173 
Yoltage calculation, 180 
[See a/so Motor Generators.] 

German Society of Electricians—Current Densities 
permissible in Copper Conductors, 149 
Glasgow Corporation Tramways, 

Generating Plant, 115 
Cost and Comparison, 133 
Plan of Power Station, 120 
Type and Capacity of Plant installed, 122 
Gottshall, W. C., on 
Tractive Resistance, 7 
Reduction, Note 11 

Increase of as a function of speed, Note 24 
Gradients, 

Braking on, 81 
Energy supplied by, 18 
Influence on 

Speed-time curves, 76, 80 
Tractive Resistance, 13 

Great Northern and City Railway—G. E. 66A 
Motor, 54 

Great Western Railway, 

Carriage Axle-box, 455 
Chambers’ Insulator, 251 
Trucks with helical axle-box Springs, 433 
Grindle on Storage battery prices, 201 


IIalpix, Droit— Comparison of power absorbed 
by locomotive and train, Note 12 
Hand firing versus Mechanical Stokers, 109 
Hay, H. A., 

Motor bogie design, 435 
Braking, 450 


Hay, H. A., contd. 

Motor bogie design, eontu. 

Play of Journal in Brass, 457 
Tyre, 461 

Heat transferred from water to air by radiation 
and evaporation, 114 
Heating, 82 

Cables, Heating of, 148 
Surface, 107 

Hedley’s Motor Truck, 441 
Brake foundation, 447, 450 
Helical Springs, Formulae for, 445 
Henley’s Patent “ Laminae ” Conductor Cable, 162 
Ileyland—Investigations on Polyphase Induction 
Motors, 392 

High Speed Electric Traction, Gearless loco¬ 
motive especially adapted to, 325 
High Tension Transmission System, see Trans¬ 
mission System 

High Yoltage Continuous Current Motors, 386 
Ilighfield, Data on Storage Battery Prices, 201 
Hubbard’s Booster-Battery Connections, 195 
Hunt Automatic Shovel, 124 

Lupedaxce of overhead circuit with rail return 
283 

Induction Motors, see Motors 
Input to train, Relation of maximum to average, 
80 

Installation of Cables, 142, 153 
Institution of Electrical Engineers—Maximum 
permissible current in Copper Conductors, 148 
Insulating Conductor Rails, 248, 251 
Insulation on Cables, 141 
Paper versus Rubber, 150 
Standard thicknesses, 162 
Insulators, 

Cable, Suspension Cables, 260 
Rail, 

Chambers’ Type, 251 
Material used, 249 

Reconstructed Granite Co.’s type, 251 
Iuterborough Rapid Transit Co., see New York 
Subway 
Iron, 

Brake Shoes of cold blast cast iron, 450 
Losses, 82 
Resistance, 246 
Italian State Railways, 

Ganz (1906) polyphase locomotives, 341 
[See also Valtellrna Railway.] 


Jet Condenser, 110 
Journals, 

Composition of bearings for coach and wagon 
journals, 455 

Friction, Energy to be employed in overcoming, 
456 

Play in Brass, 456 
Pressures, 457 


Kavaxagh, A. L., on current densities in Cables, 
149 

Kinetic Energy, 21, 80, 448 
Korbully Axle Box, 455 


INDEX 


“Laminae” Conductor Cable, Henley’s Patent, 
162 

Lamme, B. G., on 

Compensated Series Single-pbase Commutator 
Motor, 395 

Single-phase railway system, 393, Note Alb, 420, 
421 

Lancashire and Yorkshire Railway, 

Bogie Truck for Electric Motor Cars, 435 
Arrangement of Contact Devices, 453 
Braking, 450 

Method of securing Tp’e, 461 
Play of journal in brass, 457 
Experiments showing power absorbed by loco¬ 
motive compared with train, 12 
Lancashire Boilers, 107 

Langdon, W. E., on position of conductor rails, 
255 

Laugen Mono-rail System, 367 
Latour—Development of single-phase commutator 
motors, 392-4 
Lead Sheathing, 143, 162 
Standard thickness, 164 
Leakage, 

Indicators, 222 

Track Rails, Leakage from, 285 
Lincoln, P. M., on 

Single-phase system, 420 
Single-phase versus Continuous Current Equip¬ 
ments, 422 et seq. 

Live Rails, Protection of, 251 
Liverpool Overhead Railway—Tests showing 
accelerating rate, Mr. Mordey on, 31 
Load, 

Characteristics, 

Choice of motor and gear ratio, 82 
Fluctuation, 81 
Curves, 54 

Locomotives and their electrical equipment, 291 
et seq. 

Frames, 

Materia], 432 
Types, 442 
Geared, 

Baltimore and Ohio 1903Locomotive, 310,386 
Trucks, 431 

Gearless versus, 315, 325 
Paris-Orleans type, data, 319, 386 
“ Baggage Car ” type, 324 
Gearless, 

Advantages associated with greater weight 
of. 326 

Baltimore and Ohio 1896 Locomotive, data, 
307 

Trucks, 431 

Central London Railway, data, 317, 386 
Geared versus, 315, 325 
New York Central Railway, data, 292, 386 
Especially adapted to high speed electric 
traction, 325 
Tests, 298 et seq. 

Trucks, 432 

Yaltellina polyphase, 326 
Italian State Railways—Ganz 1906 polyphase 
Locomotive, 341 
Motor Cars versus, 291, 344 
Oerlikon 15,000 volt, 15 cycle equipped with 
single-phase Commutator motors, 347 


Locomotives aud their electrical equipment, contd. 
Siemens & Halske high speed 10,000 volt 
3-phase, 354 

Single phase with Continuous Current Driving 
motors, 416 
Oerlikon type, 351 
Steam, 

Electric versus Steam, 325 
Equalisers, Note 432 
New York Central ,l 999” type, 294 
[Sre also Electrical Equipment.] 

London, Brighton and South Coast Railway, 
Weight of Single-phase equipment, 390 
Winter-Eiehberg Motors, 394 
London Underground Electric Railway, 

Conductor Rails, 246 
Insulators, 250 

Metropolitan District Railway, 

Brake heads and shoes, 439, 449 
Cable construction, 158 
Conductor rails, Position of, 255 
Contact devices on truck arrangement, 453 
Forest City Bonds, 276 
Sub- station—technical data, 208 
Plan and Equipment. 225 
Trailer and Motor Bogies, 439, 441 
Metropolitan Railway, 

Cable Construction, 161 
Conductor Rails, Position of, 255 
Sub-stations—technical data, 20S 
Plan and Equipment, 223 
Weight of continuous current equipment, 390 
Long Island Railway, 255 
Losses, 55 

Copper and Iron calculations, 82 
Friction—dry versus wet air pumps, 112 
Line loss and regulation, 145 
Rheostatic, 

Effect of severity of service, 50 
Reduction by series parallel Control, 58 
Single-phase commutator motors, 415, 421 
Lyndon, Lamar, on Storage Batteries, 195, 202 


Magnetic Circuit, Saturation of, 54 
Magnetomotive force, 176 

Manganese, Effect on conductivity of steel, 248 
Manhattan Elevated Railway, 

Insulators, 250 
Motor Truck, 437 
Axle, 458 

Brake arrangement, 447 
Journal play in brass, 457 
Eeyless driving wheel, 460, 461 
Sub-station expenses, 242 
Master Mechanics’ Association—Standard axle- 
box, 454 

McDoble on Adhesion coefficient in steam and 
electric locomotives, 326 
McGuire Bogie Truck, 440 
McMahon, Mr. P. V., on 
Gear less Motors, 315 
Starting Resistance Experiments, 4 
Tractive Resistance Tests, 8 

Tests showing effect of curves on, Note 11 
Mechanical Resistance, Relation to total resist¬ 
ance, 10 

Mechanical Stokers versus hand firing, 109 


470 


INDEX 


Meraey Bailway, Method of protecting live rails, 

ZDo 

Metropolitan Railway, see London Underground 
Llectnc Railways 
Meyer on journal pressures, 4.37 
Mono-rail traction systems, Rolling Stock for 
367 

Mordey, W. M., on acceleration, 31 
Motor 

Carriages and their electrical equipment, 291 
Oars, 

A.E.Gr. High Speed Zossen, 362 
Electric Locomotives versus, 291, 344 
Siemens & Halske High Speed Zossen, 362 
Valtellina Railway, 343 
< Characteristics, 

Average profile of the line, S3 
Electric Railway Motors, 54 
Control, see Control System 
Carve, Acceleration on, 25, 32, 48, 62, 66, 73 
Generators, 

Economic advantage of, 188 
Oerlikon single-phase locomotive with con¬ 
tinuous current driving motor, 351, 416 
Rotary Converters versus, 173, 186, 189 
Starting of Asynchronous motor generator 
sets, 208 

Motor driven air compressor, 3*t6 
Motors, 

Alternating Current, 

Losses in transformers and potential regula¬ 
tors, 56 

[.See also Motors, Single-phase, Polyphase and 
Synchronous.] 

Continuous Current, 

Electrical equipment data, 88, 94 
High voltage, employment of, 386 
Losses in external resistances, 56 
Schedule speed, 29 
Series motor, 

Characteristics, 32 
G.E. 66 A, 54 ct seq. 

Variation in design, 54 
Weight Coefficient, 373 
Geared versus gearless, 315, 432 
Induction, 

Employment for driving continuous current 
generators, 173 

10,000 volt three-phase motors for Siemens & 
Halske Locomotive, 355 
Method of attaching to bogie, 451 
Hew York Central Locomotive, Motor for, 294 
Nose versus Centre of Gravity method of sus¬ 
pending, 451 

Polyphase Induction, 391 
Disadvantages, 392 
Rating of Railway Motors, 55, 87 
Single-Phase Commutator, 

Compensated series type, 395 
G.E.A. 605, 75h.p. Motor, Description, 396 
Component Losses, Summary, Note 421 
Development, 390 

Inferiority to Continuous Current Motor, 415 
Latour-Winter-Eichberg type, 393, 394, 

417, 418, 422 

Oerlikon 15,000-volt, 15-cycle locomotive 
equipped with, 347 
Repulsion type, 393 


Motors, contd. 

Single-phase and Continuous current, weight 
388 & ’ 

Size dependent upon gear ratio, diameter of 
wheels, etc., 82 
Synchronous 

Employment for driving Continuous current 
generators, 173 
Phase characteristics, 174 
Y-connected, 177 
Mounting of Conductor Rails, 248 


National Conduit and Cable Co. of New York, 
Cables furnished to Central London Railway 
156 J 

C urrent Densities, Conditions for three-core 
Cables, 149 

Neptune Rail Bond, 277 

New York Central and Hudson River Railroad, 5 
Conductor Rails, Under contact 3rd rail, 250 
254 

Insulators, 250 

Live load percentage, 13 

Locomotive, 

Electric, data, 292, 386 
Especially adapted to high speed electric 
traction, 325 

Tests, 298—Steam versus Electric, 301 
Trucks, 432 

Steam “ 999 ” type, 294 
Steel Tower for supporting overhead portion of 
transmission line, 171 
Sub-stations, technical data, 208 
Plan and equipment, 232 
New York Subway 

Cable Construction, 154 
Method of protecting live rails, 253 
Sub-stations—Technical data, 208 
Plan and equipment, 238 
North Eastern Railway, 

Bogie truck for electric motor cars, 434 
Arrangement of Contact Devices, 453 
Brake foundation, 447, 450 
Goods locomotive frame, 433 
Sub-stations—technical data, 208 
Plan and equipment, 229 


Oerlikon Co. 

Motor Generator type of single phase locomo¬ 
tive with continuous current driving motors, 
351, 416 

Switch, Overhead high tension, 354 

Track boosters, 284 

15,000 volt, 15 cycle locomotive with single 
phase Commutator motor, 347 
O’Gorman on Insulation on Cables, 142, 187 
Oil-cooled Compressor, 402 

Output—Single-phase versus continuous current 

motors, 417 
Overhead System, 258 

Alternating and continuous current systems, 
245 

Construction of conductor and supports, 162 

Contact collecting Devices of New York Central 
locomotive, 297 


47i 


INDEX 


Overhead System, contd. 

High Tension Lines, 

Calculation of, 164 
Steel Tower for supporting, 171 
Suspension Cables, 259 
Third Rail System versus, 244 

Pantograph Trolley, 414 
Paper versus Rubber Insulation, 150 
Parallel Control versus Series Parallel Control, 74 
Paris Metropolitan Motor Car with rigid wheel 
base, 430 

Paris-Orleans Railway, 

Geared Electric Locomotive, data, 319, 386 
“Baggage Car’’ type, 324 
Method of protecting live rails, 253 
Mounting and insulating conductor rails, 251 
Parry, E., on Distribution of Current Density, 285 
Parshall, 

Motor Bogie for Central London Railway, 439 
Brake arrangement, 441, 447, 450 
Switchgear, 213 

Passenger Weight, percentage of total train 
weight, 12 

Pennsylvania Railway, see Wilkesbarre and 
Hazelton Railroad 

Periodicity for Alternating Current, 416 
Permanent Way, Effect of high accelerating rates, 
32, 90 

Perrine and Baum, 171 
Play of journal in brass, 456 
Pneumatic control connection of rheostat, 335 
Polyphase induction motors, see Motors 
Polyphase transmission systems with rotary con¬ 
verter sub-stations, 190 
Potential Regulators, Losses, 56 
Power, 

Amount required during acceleration, 30 
Axles, Power at, 40 et seq. 

Maximum instantaneous power required at 
axles, 44, -19 

Percentage absorbed by locomotive and train, 
12 

Ratio of maximum to average power at axles— 
Steam versus electric service, 51 
Power factor of single-phase motors, 418, 422 
Power Station, 

Arrangement of Plant, 107 
Bristol Tramways, 115, 124 
Central London Railway, 115, 133 
Dublin United Tramways, 115, 127, 133 
Efficiencies of English and foreign, 134 
Glasgow Corporation Tramways, 115, 120, 133 
Ratio between maximum and average input to 
train, Effect on, 80 
Thermal efficiencies of Plant, 136 
10,000 k.w. turbine station, 130 
Pressures, Journal, 457 
Profile of the Line, 83 
Pumps, 

Air, 

Dry and wet, 112 
Edwards’ type, 118 
Centrifugal versus reciprocating, 111 

Radiation —Heat transferred from water to air 
by, 114 


Rail, 

Bonds, 273 

Resistance data, 279 
Soldered, 278 
Insulators, see Insulators 
Rails, 

Conductor, 246 
Channel Rail, 251 
Data for various railways, 249 
Mounting and insulating, 248 
Overhead System, 258 
Position, 254 

Protection of live rails, 251 
Resistance to alternating currents, 280 
Under-contact type, 254, 302 
Track, 

Basic open-hearth, 269 
Bessemer steel rails, 269 
Bull-head rail, Standardization, 270 
Composition and Conductivity, 245, 267 
Conductor Rails versus, 246 
Leakage from, 285 
Resistance tests, 270 
[See also Third Rail System.] 

Railton and Campbell Filters, 126 
Railways, 

Steam versus Electric, 13, 29, 34, 51, 88 
[See also Names of Railways.] 

Rankin’s Formulae for design of helical springs, 
445 

Rating of railway motors, 55, 87 
Reciprocating Engines versus steam turbines, 101, 
103, 113 

Reciprocating versus centrifugal pumps, 111 
Reconstructed Granite Co.’s types of Insulator, 
251 

Regenerative Control System, see Control 
System 

Regenerative features observed at Valtellina, 
33S 

Reichel—Advocate of continuous current motors, 
Note 392 

Repulsion type of single-phase commutator 
motors, 393 
Resistance, 

Air—Relation to total, 10 
Liquid starting, 74 
Loss in external resistance, 56 
Rail, 246 

Alternating Currents, resistance of rails to, 
2S0 

Tests, 270 

Rail bonds, data, 279 
Tractive, 61 

Air and mechanical components, 10 
Aspinall on, 4 et seq. 

Berlin-Zossen tests, 5 et seq. 

Camp’s Resume, Note 6 

Comparison between heavily loaded and light 
trains, 11 

Curves, Influence on, 11, 13 

Energy required to overcome, 18 

Gradients, Influence on, 13 

Influence of uncontrollable factors, 3, 5, 13 

Internal and external, 63 

Reduction of, 10 

Starting resistance, 4 

Tractive resistance at constant speed, 3 


472 


INDEX 


Retaliation, Rate during braking, 23 
Rheostatic Losses, see Losses 
Rheostats, Metallic and Water—Pneumatic con¬ 
trol connections for Yaltellina “1904” loco¬ 
motive, 335 
Rivets, 440, 443 
Rolling Stock, 

Acceleration, Effect of high rate on, 32 
Data for various railway coaches, 14 
Mono Rail Traction Systems, 367 
Trucks, 430 et seq. 

Valtellina Railway, 343 
Rotary Converters, 

Central London Railway, 217 
Comparative Costs, 189 
Line Loss and regulation, 145 
Motor Generators versus, 173 

Central London Railway sub-station, 1S6 
Phase characteristics, 177 
Series winding, 186 
Shunt excited, 1S4 
Six-phase, 177 
Employment, 172 
Synchronising and switching, 206 
Starting and synchronising of, 204 
Three-phase, 

Connection with compensator, 204 
Magnetomotive force of armatures, 177 
Synchronising and switching, 206 
Rubber versus Paper Insulation, 150 


Sajiuelson’s three-phase switch, 216 
Saturation of magnetic circuit, 54 
Schedule speed, see Speed. 

Schoepf—Weights of continuous current and 
single-phase motor equipments, 389, 390 
Series parallel control, see Control System 
Shawmut Soldered Rail Bonds, 278 
Shunt excitation—Effect of operating the rotary 
converter with, 184 
Siemens on Contour of Car, Note 11 
Siemens Bros., City and South London Gearless 
Locomotive, 317 
Siemens & Halske, 

High Speed Zossen Motor Car, 362 
High Speed 10,000-volt 3-phase locomotive, 
354 

Single Phase Commutator Motors, see Motors 
Single Phase and Continuous Current System, 95, 
360, 386, 419 
Carter on, 242 

Comparative capital and operating costs, 425 
Deterioration of commutator, 97 
Smith, W. M., on Comparison of power absorbed 
by locomotive and train, Note 12 
Soldered rail bonds, 278 
Speed 

Average speed, 28, Note 91 
Effect of gear ratio on, 82 
Schedule speed, 

Continuous current motors, 29 
Designation, 28, Note 91 
Limitations, 34 
Steam versus Electricity, 88 
Sprague, E. J., on Alternating and continuous 
current operation, 360 


Sprague, General Electric type of controlling 
appliances, 296 
Springs, 

Helical, Formulae for, 445 
Semi-elliptical, Formulae for, 445 
Steam, 

Economy—Turbine versus reciprocating engines, 

Locomotives, see Locomotives. 

Piping arrangement, 107 
Railways, 

Axle-box, type of, 455 
Motor bogie truck design, 433 
Turbines, see Turbines. 

Steam versus electric service, 13, 29, 34, 51, 88, 325 
New York Central Railway Tests, 301 
Valtellina Railway, 344 
Steel 

Axles, qualities for, 460 
Brake heads, cast steel for, 450 
Conductivity of, 247 
Locomotive frames, 

Soft cast steel, 441 
Steel plate for, 432 

Tower for supporting overhead high tension 
transmission lines, 171 
Track rails, 269 
Tyres, Qualities for, 462 
Stewart, Mr.—Cost of Cables, 187 
Stone’s bronze alloy 456 
Storage Batteries, 

Auxiliaries—Battery-booster set, 192 
Modifications, 195 

Comparison of price in Germany, England and 
America, 201 

New York Central Railway Equipments, 236 
Storer on Series versus Parallel Control, 76 
Stresses, Axle, 458 
Sub-stations, 172 

Accumulators, Use of in, 191 

Comparative costs of Plant with and without 
accumulators, 200 
Capacity of Machinery, 242 
Central London Railway, 208, 212 

Rotary Converters versus Motor Generators, 
186 

Continuous Current Generators, 173 
Cost of Plant, 198 

Description of extensive tramway plant in 
South America, 188 
Design, 203 

Equipment of, for New York Central Locomo¬ 
tive tests, 299 
Location, 241 

Metropolitan District Railway, 208, 225 
Metropolitan Railway, 208, 223 
New York Central and Hudson River Railroad, 
208, 232 

New York Subway, 208, 238 
North Eastern Railway, 208, 229 
Polyphase Transmission systems with rotary 
converter sub-stations, 190 
Rotary Converters, 145 
Transforming apparatus, 172 
Superheating, Advantages, 108 
Surface Condenser, 110 

Suspension—Nose versus Centre of gravity sus 
pension of motors, 451 


4 73 


INDEX 


Suspension Cables, 259 
Copper Conductors, 260 
Insulators, 260 
Switches, 

Electro-pneumatically controlled unit switches, 
411 

Oerlikon overhead high tension, 354 
Switchgear, arrangement of, 203 
Swivelling of Bogie, 443 
Synchronous Motors, see Motors 
Synchroscope on District Bailway, 227 
Szasz on Efficiency in single-phase commutator 
motors, 421 

Teich muller’s formulae for calculating permis¬ 
sible current densities, 149 
Temperature, 

Distribution in Cables, 149 
Bise, 

Cables, 148 

Method of estimating, 82 
Third Bail System, 246 

Baltimore and Ohio 1896 Gearless Locomotive, 
309 

Overhead System versus, 244 
Paris-Orleans Line, 323 
Shoe of New York Central Locomotive, 297 
Under-contact rail, advantages, 254, 302 
Thomas’ Soldei’ed Bail Bonds, 278 
Thompson, Elihu—Bepulsion Motor, 393 
Three-phase continuous current system, Sub¬ 
station, 172 

Track, Experimental track for New York Central 
locomotive tests, 298, 302 
Track Bails, see Bails 
Tractive 
Effort, 

Effect of gear ratio on, 82 
Light versus heavy trains, 86 
Force, Power and Energy at Axles, 40 et seq. 
Besistance, see Besistance 
Tramway Plant—Description of extensive plant 
in South America, 188 
Tramways, 

Conductor, Method of suspending, 258 
Spare Generating Plant, 103 
Transformers, 

Losses, 56 

Motor Generators, 173 
Static, 172 

200 kilovolt ampere air blast, 347 
Transmission System, 140 

Cables, cost, construction, etc., 141 
New York Central Locomotive, special line for 
tests, 299 

Overhead lines, calculation of, 164 
Botary Converter sub-stations, 190 
Single-phase system, spare line for, Note 426 
Steel tower, 171 
Trolley, 

Oerlikon overhead, 354 
Self-reversing Pantograph type, 414 
Trucks, Bogie, 430 et seq. 

Axle, 

Boxes, 453 
Guards, 435 

Baltimore and Ohio Bail way, 431 
Brake work, 445 et seq 


Trucks, Bogie, contd. 

Brill type, 435, 441 
Built up steel frame, description, 434 
Central London Bailway, 438 
Motor and trailer brake blocks, 449 
Parshall’s, design, 439, 441, 447 
City and South London Bail way, 431 
Composition of bearings for coach and wagon 
journals, 455 
District Bailway, 439, 441 
Effect of high accelerating rates, 90 
Electrical contact devices, arrangement of, 
453 

Equalising lever, 432 
European and American types, 433 
Frame types, 441 
Hedley’s motor truck, 441, 447 
Journals, play in brass, 456 
Lancashire and Yorkshire Bailway, 435 
Brake work, 450 

Manhattan Elevated Bailway, 437, 447 
Material suitable, 432 
Method of attaching motors to bogie, 451 
New York Central Bailway, 432 
North Eastern Bailway, 434 
Brake work, 450 

Bivets preferable to bolts, 440, 443 
Springs, 444 

Steel, Employment of, 441 
Swing and rigid bolsters, 434 
Valtellina Motor Cars, 343 
Tube Bailways, 

High Tractive Besistance, 8 
[See also names of Bailways.] 

Turbine, 

Generator for operating New York Central 
Locomotive, 298 

Plan of 10,000 k.w. power station, 130 
Beciprocating engines versus, 101, 103, 113 
Tyres, 461 

Under. Contact Third Bail System, see Third Bail 
System 

Unit Switches, Electro-pneumatically Controlled, 
411 

Valatin’s data for railway motors, 373 
Valtellina Bailway, 

Liquid Starting Besistances, 74 
Locomotives, three-phase gearless, 326 
Motor Cars, 343 
Begenerative features, 338 
Steam versus electric traction, 344 
Venturi Water Meter, 118 

Verbaud Deutscher Elektrotechniker, Formulae 
for calculating permissible Current Densities, 
149 

Voltage, 

Continuous Current Motors, 386 
Drop in uninsulated conductors, Board of Trade 
Bestrictions, 241 
Effect on cost of cables, 145 
Method of calculating generator voltages, 180 
Transforming apparatus, 172 

Ward-Leonard System of motor control, 351 
Water-tube boilers, 107 


474 


INDEX 


Weight, 

Electrical Equipment, 29, 43 
Geared versus Gearless equipment, 372 
Loaded train, 7 
Motor ou axles, 451 

Percentage of passenger and freight weight to 
total train weight, 12 
Pailway Motors, 373 

Patio between dead and told weight of car, 13 
Westinghouse Company, 

Exhibition car, 414 
Oil Break High Tension Switches, 230 
Overhead Conductor and supports, 263 
Standard single-phase railway motor, 405 
Weston Bros. Leakage Indicators, 222 
Wheel (s), 

Attachment to axles, 460 
Centres, 461 
Diameter, 82 


Wheel(s), contd. 

Doyle and Brinckerhoff’s keyless wheel, 460 461 
Potational energy of, 21 

Wilkesbarre and Hazelton Railroad, Pennsyl¬ 
vania, J 




Position of conductor rails, 255 
M ilson. Prof., on Electrical and magnetic proper¬ 
ties of track, 281 
Wind Resistance, 11 

A inter-Eichberg type of single-phase Commuta¬ 
tor Motors, 393, 394, 417, 418, 422 

A ood, Inferiority of to other insulating materials 
251 


Worsdell, W. —Motor bogie design, 434 
Brake foundation, 447, 450 
M vnne, Tractive Resistance Curves, 87 


Zossen-Berlin, sec Berlin-Zossen Tests 


BRADBURY, AGNEW, <fc CO. LD., PRINTERS, LONDON AND TONBRIDGE. 






























































































